[5] Zimonjić turned pro in 1995 and remained relatively unknown outside his native country until a surprise victory in the mixed doubles at the 2004 Australian Open.

Paired for the first time with Russian Elena Bovina, he beat defending champions Martina Navratilova and Leander Paes in straight sets in an hour and nine minutes.

Alongside Katarina Srebotnik of Slovenia, he won the 2006 French Open crown with a straight-sets victory over Daniel Nestor and Elena Likhovtseva.

In 2007, Zimonjić reached the 2007 French Open mixed doubles final as the defending champions with Katarina Srebotnik and lost to Nathalie Dechy and Andy Ram.

With Victor Troicki, he won two decisive games against Italian and Argentinian teams; as a result, Serbia finished first in its group, and then proceeded to beat Germany in the final encounter.

In 2015 he started the year partnering Aisam-ul-Haq Qureshi, then teamed up with Marcin Matkowski; despite not winning a title together, the Polish-Serbian duo qualified for the World Tour Finals.

[9] He returned to the ATP tour in February 2019 at the Sofia Open, where he and compatriot Viktor Troicki had won the doubles title two years prior.

He went on to win four other ITF satellite events, as well as four Challenger tour titles in singles: Kyiv (Ukraine) in 1998, Belo Horizonte (Brazil) in 2000, Andrezieux (France) in 2001, and Belgrade (Serbia) in 2004.

In recent years, with the emergence of highly ranked Serbian singles players Novak Djokovic, Janko Tipsarević, and Viktor Troicki, Zimonjić became a doubles specialist on the team, partnering all of them, as well as Dušan Vemić and Ilija Bozoljac.

In 2010, Serbia won its first ever Davis Cup title, following the victories over United States (3–2), Croatia (4–1), Czech Republic (3–2), and France in the final match (3–2).

The central celebration was held in Belgrade in front of several thousand fans, and the Serbian national postal service issued a stamp picturing the players.

[15] Zimonjić was named Serbia Davis Cup team captain in 2003-2004 and from January 2017 till December 2020 when he was unexpectedly replaced by Victor Troicki.

Zimonjić's paternal family hails from the Gacko region in Herzegovina, from where it settled in Vučkovica near Kragujevac, while his mother was born in Gospić, in Lika.