<PAGE>   1


                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                          ---------------------------


                                    FORM 8-K

                                 CURRENT REPORT

                       Pursuant to Section 13 or 15(d) of
                      The Securities Exchange Act of 1934
                          ---------------------------


         Date of Report (Date of earliest event reported): June 1, 1998

                         MERRILL LYNCH DEPOSITOR, INC.
           (ON BEHALF OF PUBLIC STEERS(R) SERIES 1998 IBM Z-2 TRUST)
             (Exact name of registrant as specified in its charter)

        DELAWARE             333-29015            13-3891329
      (State or other       (Commission         (I.R.S. Employer
      jurisdiction of        File Number)       Identification No.)
      incorporation)

  WORLD FINANCIAL CENTER,                        10281
   NEW YORK, NEW YORK                          (Zip Code)
    (Address of principal
     executive offices)

                          ---------------------------

       Registrant's telephone number, including area code: (212)449-1000

                      INFORMATION TO BE INCLUDED IN REPORT

ITEM 1.           CHANGES IN CONTROL OF REGISTRANT

                  Not Applicable

ITEM 2.           ACQUISITION OF DISPOSITION OF ASSETS

                  Not Applicable

ITEM 3.           BANKRUPTCY OR RECEIVERSHIP

                  Not Applicable

ITEM 4.           CHANGES IN REGISTRANT'S CERTIFYING ACCOUNTANT

                  Not Applicable




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ITEM 5.           OTHER EVENTS

                  99.1 Distribution to holders of the Public STEERS(R) Series 
                  1998 IBM Z-2 Trust Class A Certificates on June 1, 1998.

ITEM 6.           RESIGNATION OF REGISTRANT'S DIRECTORS

                  Not Applicable

ITEM 7.           FINANCIAL STATEMENTS AND EXHIBITS

                  (a) Financial statements of business acquired

                      Not applicable

                  (b) Pro forma financial information

                      Not applicable

                  (c) Exhibits

                     99.1 Trustee's report in respect of the June 1, 1998 
                          distribution to holders of the Public STEERS(R)
                          Series 1998 IBM Z-2 Trust Class A Certificates.

ITEM 8.           CHANGE IN FISCAL YEAR

                  Not Applicable

ITEM 9.           SALES OF EQUITY SECURITIES PURSUANT TO REGULATION S

                  Not Applicable

                                    SIGNATURES

                  Pursuant to the requirements of the Securities Exchange
                  Act of 1934, the registrant has duly caused this report
                  to be signed on its behalf by the undersigned, hereunto
                  duly authorized.


                                    MERRILL LYNCH DEPOSITOR INC.

           Date:                    By:

                                       Name:  Frank D. Ronan
                                       Title: President
<PAGE>   3
                                 EXHIBIT INDEX


99.1   Trustee's report in respect of the June 1, 1998 distribution to holders
       of the Public STEERS(R) Series 1998 IBM Z-2 Trust Class A Certificates.
<PAGE>   4
                                  EXHIBIT 99.1

                              DISTRIBUTION REPORT
                                      FOR
                   PUBLIC STEERS(R) SERIES 1998 IBM Z-2 TRUST

                               DISTRIBUTION DATE
                                  JUNE 1, 1998

(i)    the amounts received by the Trustee as of the last such statement in
       respect of principal, interest and premium on the International Business
       Machines Corporation Debentures due 2096 (the "Underlying Securities"):

<TABLE>
<S>                                         <C>
                    Interest:                $3,384,375.00
                    Principal:               0.00
                    Premium:                 0.00
</TABLE>

(ii)   the amounts of compensation received by the Trustee, for the period
       relating to such Distribution Date:

<TABLE>
<S>                                          <C>
                    Paid by the Trust:       $879.05
                    Paid by the Depositor:   $120.95
</TABLE>

(iii)  the amount of distribution on such Distribution Date to Holders allocable
       to principal of and premium, if any, and interest on the Certificates of
       each such Class and the amount of aggregate unpaid interest accrued as of
       such Distribution Date:

<TABLE>
<S>                                          <C>
               Class A:
                    Interest:                $2,456,495.95
                    Principal:                 $927,000.00

               Class B:
                    Interest:                         0.00
                    Principal:                        0.00

                    Unpaid Interest Accrued:          0.00
</TABLE>

(iv)   the aggregate stated principal amount and, if applicable, notional amount
       of the Underlying Securities related to such Series, the current interest
       rate or rates thereon at the close of business on such Distribution Date,
       and the current rating assigned to the Certificates.

<TABLE>
<S>                                         <C>
                    Principal Amount:       $95,000,000
                    Interest Rate:          7.125%
</TABLE>
                    Rating:
                         Moody's Investor Service           A1
                         Standard & Poor's Rating Service   A
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(v)  the aggregate Certificate Principal Balance (or Notional Amount, if
     applicable) of each Class of such Series at the close of business on such
     Distribution Date.



     Class A:                             
     Initial Principal Balance:         $76,586,000
     Reduction:                           ($927,000)
                                        -----------
     Principal Balance 6/1/98:          $75,659,000


     Class B:              
     Principal Balance at Maturity:     $95,000,000