In 2004, he defeated Andre Agassi in St Pölten, and in 2005 on the grass of Halle, he defeated Nicolas Kiefer.
Zimonjić has been a member of Serbia Davis Cup team (previously Yugoslavia Davis Cup team and Serbia and Montenegro Davis Cup team, respectively) since 1995, playing both singles and doubles, and in 2003-2004 he was the playing captain of the national team.