Document:

<PAGE>

                                                                   EXHIBIT 10.52

            FORM OF AGREEMENT TO BE BOUND BY REGISTRATION AGREEMENT
            -------------------------------------------------------

     The undersigned, [insert the name of each entity and individual who is
become a party to the Registration Agreement], hereby certify to, and agree with
ZC Acquisition Corp, a Delaware corporation ("ZC Corp"), as follows:

     1.  The undersigned have each read a copy of that certain Registration
Agreement, dated March 23, 1999 (the "Registration Agreement"), by and among ZC
Corp, CTCR Fund VI, L.P., a Delaware limited partnership, CTCR VI Executive
Fund, L.P., a Delaware limited partnership, GTCR Associates VI, a Delaware
general partnership, William Seibel and any other executive employees of ZC Corp
or other entities and individuals who, at any time, acquire securities of ZC
Corp in accordance with Section 8 of the Registration Agreement

     2.  The undersigned agree that their signatures below shall constitute an
executed counterpart signature page to the Registration Agreement and that they
shall succeed to all of the rights and obligations of an "Other Stockholder"
under the Registration Agreement as contemplated by Section 8 of the
Registration agreement.

     Executed this ____ day of _______________, _____.

[Insert a signature line for each entity and individual who is becoming a party
to the Registration Agreement]

     As required by Section 8 of the Registration Agreement referred to above,
the undersigned hereby consents to [insert the name of each entity and
individual who is becoming a party to the Registration Agreement] succeeding to
all of the rights and obligations of an "Other Stockholder" under such
Registration Agreement.

                                                GTCR FUND VI, L.P.
                                                By:   GTCR Partners VI, L.P.
                                                Its:  General Partner

                                                By:   GTCR Golder Rauner, LLC
                                                Its:  General Partner

                                                By:   _________________________
                                                Its:  Principal
<PAGE>

     The foregoing agreement was entered into between ZEFER Corp. and the
following stockholders as of the date set forth opposite each stockholders'
name:

     1261417 Ontario Limited, April 30, 1999
     Matthew P. Burkley, April 30, 1999
     Ian R. Colliety, April 30, 1999
     Stephen R. DiMarco, April 30, 1999
     Deborah E. Frieze, April 30, 1999
     Edmond C. Jay, April 30, 1999
     Alexandre Scherer, April 30, 1999
     Kaming Ng, April 30, 1999
     Anthony K. Tjan, April 30, 1999
     Gregory S. Hipwell, May 14, 1999
     Jason J. Zada, May 14, 1999
     Renaissance Worldwide, Inc., May 28, 1999
     Allan L. Cohen, September 13, 1999
     Fred Luconi, September 13, 1999
     Thomas J. Waite, September 13, 1999<PAGE>

                                                                   EXHIBIT 10.53

            FORM OF AMENDMENT TO RESTRICTED STOCK VESTING SCHEDULE

                           [ZEFER Corp. Letterhead]

                                           March __, 2000

  [Name of Party]
[Address of Party]

     Re:  Amendment to Senior Management Agreement

Dear [Name of Party]:

     This letter agreement amends that certain [insert the type of agreement to
be amended] (the "Agreement") dated as of [date of the relevant agreement with
the Party] between you, ZEFER Corp. (the "Company"), GTCR Fund VI, L.P., GTCR
Executive Fund VI, L.P., and GTCR Associates Fund VI, L.P. (collectively, the
"GTCR Affiliates").

     Section 2 of the Agreement is hereby amended as follows:

1.   Amendment to Section 2(a). Section 2(a) of the agreement is hereby amended
     --------------------------
     and modified by replacing the second sentence thereof with the following"

     "Except as otherwise provided in Sections 2(b), 2(c) and 2(d) below, the
     Executive Stock will become vested in accordance with the following
     schedule (the "Vesting Schedule"), if as of each such date Executive is
                    ----------------
     still employed by the Company or any of its Subsidiaries.

2.   Amendment to Section 2(d). Section of the Agreement is hereby amended and
     --------------------------
     modified by adding the following subsection:

     "(d)  In the event that William A. Seibel is no longer serving as the
     President or Chief Executive Officer of the Company, and (i) the Company
     terminates the Executive's employment without Cause or (ii) the Executive
     resigns from his/her position with the Company for Good Reason, then all
     shares of Executive Stock which have not yet vested shall automatically
     vest one business day prior to the time of such event and such shares shall
     not be subject to the provisions of Section 3 hereof.

3.   General.  Except as specifically modified and amended hereby, the Agreement
     --------
     remains in full force and effect and is hereby ratified, confirmed and
     approved in all respects. This Letter Agreement reflects the complete
     agreement and
<PAGE>

     understanding among the parties and supersede and preempt any prior
     understandings, agreements or representations by or among the parties,
     written or oral, which may have related to the subject matter hereof in any
     way. This Letter Agreement may be executed in separate counterparts, each
     of which is deemed to be an original and all of which taken together
     constitute one and the same agreement. The laws of Delaware shall govern
     all issues concerning the relative rights of the Company and its
     stockholders and all other questions concerning the construction, validity
     and interpretation of this Letter Agreement, without giving effect to any
     choice of law or other conflict of law provision or rule (whether of the
     State of Delaware or any other jurisdiction) that would cause the
     application of the laws of any jurisdiction other than the State of
     Delaware.

     IN WITNESS WHEREOF, the parties hereto have executed this Senior Management
Agreement on the date first written above.

                              ZEFER CORP.

                              By:________________________________
                              Its:

                              ___________________________________
                              Executive

Agreed and Accepted:

GTCR FUND VI, L.P.

By:  GTCR Partners VI, L.P.
Its: General Partner
By:  GTCR Golder Rauner, L.L.C.
Its: General Partner

By:   _________________________________
Name: _________________________________
Its:  Principal

GTCR VI EXECUTIVE FUND, L.P.
By:  GTCR Partners VI, L.P.
Its: General Partner
<PAGE>

By:  GTCR Golder Rauner, L.L.C.
Its: General Partner

By:   __________________________________
Name: __________________________________
Its:  Principal

GTCR ASSOCIATES VI
By:  GTCR Partners VI, L.P.
Its: Managing General Partner

By:  GTCR Golder Rauner, L.L.C.
Its: General Partner

By:   ____________________________
Name: ____________________________
      Its: Principal

      The foregoing Letter Agreement was entered into between ZEFER Corp. and
the following stockholders of ZEFER Corp. to modify the type of agreement, and
on a certain date set forth opposite such stockholders' name:

Amendments to Senior Management Agreements

      Diedre Aubuchon, 3/13/2000
      Allan Cohen, 3/13/2000
      Gerard E. Dube, 3/13/2000
      John Kelly, 3/13/2000
      Sean W. Mullaney, 3/13/2000
      William Seibel, 3/13/2000
      James L. Slamp, 3/13/2000
      Martha Stephens, 3/13/2000
      Frank Torbey, 3/13/2000
      Thomas Waite, 3/13/2000

Amendments to Employment Agreements

      Anthony Tjan, 3/13/2000<PAGE>

                                                                   EXHIBIT 10.54

                FIRST AMENDMENT TO SENIOR MANAGEMENT AGREEMENT
                ----------------------------------------------

          THIS FIRST AMENDMENT TO SENIOR MANAGEMENT AGREEMENT (this "Amendment")
                                                                     ---------
is made of January 10, 2000, between ZEFER Corp., a Delaware corporation (the
"Company"), and William Seibel ("Executive").  Except as otherwise indicated
--------                         ---------
herein, capitalized terms used and not otherwise defined herein shall have the
meanings ascribed to such terms in the Purchase Agreement (as defined below).

          WHEREAS, the parties to this Amendment are all of the parties to that
certain Senior Management Agreement, dated as of March 23, 1999, between the
Company and Executive (the "Senior Management Agreement");
                            ---------------------------

          WHEREAS, the parties hereto desire to make certain amendments to the
Purchase Agreement in accordance with Section 12(i) thereof; and

          NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto agree as
follows:

     Section 1.  Amendments to Senior Management Agreement.
                 -----------------------------------------
          1A.  Section 2(a) of the Senior Management Agreement shall be amended
     and restated in its entirety as follows:

                 (a) All of the shares of Executive Stock acquired hereunder
          shall be subject to vesting in the manner specified in this Section 2.
          Except as otherwise provided in Sections 2(b) and 2(c) below,
          commencing on the day immediately following the Closing and continuing
          so long as Executive is still employed by the Company or any of its
          Subsidiaries, the Executive Stock will vest daily on a pro rata basis
          so that 100% of the Executive Stock will be vested on the 5th
          Anniversary of the Closing (the "Vesting Schedule").
                                           ----------------

          1B.  Section 2(b) of the Senior Management Agreement shall be amended
     and restated in its entirety as follows:

                 (b) In the event the Company consummates its initial Public
          Offering prior to the 1st Anniversary of the Closing, the Vesting
          Schedule shall be modified such that, so long as Executive is still
          employed by the Company or any of its Subsidiaries, the shares of
          Executive Stock will vest as follows: (i) 33% of the Executive Stock
          will vest upon the occurrence of such Public Offering, and (ii)
          commencing on the day immediately following such Public Offering, the
          remaining unvested shares of Executive Stock will vest daily on a pro
          rata basis so that 100% of the Executive Stock will be vested on the
          5th Anniversary of the Closing. In the event the Company consummates
          its initial Public Offering after the 1st Anniversary of the Closing
          but prior to the 2nd Anniversary of the Closing, the Vesting Schedule
          shall be modified such that, so long as Executive is still employed by
          the Company or any of its Subsidiaries, the shares of Executive Stock
          that are unvested immediately prior to such initial Public Offering
          will vest as follows: (i) an additional number of shares of Executive
          Stock will vest upon the
<PAGE>

          occurrence of such Public Offering so that 33% of the Executive Stock
          will be vested immediately thereafter, (ii) commencing on the day
          immediately following such Public Offering and continuing until the
          2nd Anniversary of the Closing, an additional number of shares of
          Executive Stock will vest daily on a pro rata basis so that 40% of the
          Executive Stock will be vested on the 2nd Anniversary of the Closing,
          and (iii) commencing on the day immediately following the 2nd
          Anniversary of the Closing, the remaining unvested shares of Executive
          Stock will vest daily on a pro rata basis so that100% of the Executive
          Stock will be vested on the 5th Anniversary of the Closing.

     Section 2. Retroactive Application of Amended and Restated Vesting
                -------------------------------------------------------
Schedule. The amendment set forth in Section 1A above shall be applied
--------
retroactively so as to cause the Executive Stock to be subject to the amended
and restated Vesting Schedule as of March 23, 1999.

     Section 3. Limitations. Except as expressly amended by this Amendment, all
                -----------
of the terms and provisions of the Senior Management Agreement shall remain in
full force and effect. This Amendment supersedes and preempts any prior
understandings, agreements or representations by or between the parties, written
or oral, which may have related to the subject matter hereof in any way.

                                  *  *  *  *

                                       2
<PAGE>

             IN WITNESS WHEREOF, the parties hereto have executed this First
Amendment to Senior Management Agreement on the date first written above.

                                          ZEFER Corp.
                                          By:  /s/ William Seibel
                                               -------------------------------
                                          Its: President

                                           -----------------------------------
                                           William Seibel

Agreed and Accepted:

GTCR FUND VI, L.P.
By:       GTCR Partners VI, L.P.
Its:      General Partner
By:       GTCR Golder Rauner, L.L.C.
Its:      General Partner

By:       /s/ Philip Canfield
          ---------------------------------
Name:
          ---------------------------------
Its:      Principal

GTCR VI EXECUTIVE FUND, L.P.
By:       GTCR Partners VI, L.P.
Its:      General Partner
By:       GTCR Golder Rauner, L.L.C.
Its:      General Partner

By:       /s/ Philip Canfield
          ---------------------------------
Name:
          ---------------------------------
Its:      Principal

GTCR ASSOCIATES VI
By:       GTCR Partners VI, L.P.
Its:      General Partner
By:       GTCR Golder Rauner, L.L.C.
Its:      General Partner

By:       /s/ Philip Canfield
          ---------------------------------
Name:
          ---------------------------------
Its:      Principal

                       SIGNATURE PAGE TO FIRST AMENDMENT
                        TO SENIOR MANAGEMENT AGREEMENT

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00003-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00003-of-00352.parquet"}], [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00003-of-00352.parquet"}]]