Complex sentence: He served as the Secretary of the Department of the Treasury from 2001 to 2011, first appointed by Liberal Party Treasurer Peter Costello in April 2001, reappointed by Costello in 2006, and retained by the Rudd government.
Split into simpler sentences: He served as the Secretary of the Department of the Treasury from 2001 to 2011. He was first appointed as Treasury Secretary by Liberal Party Treasurer Peter Costello in April 2001, and reappointed by Costello in 2006, and retained by the Rudd government.