He has won seven professional singles titles (and numerous doubles titles) in his career, starting with back-to-back satellite wins in El Salvador on hard court, followed by a win in Honduras on red clay. Fleishman then won back-to-back titles again, this time in his native California, winning two futures events in Redding and Chico (he also won the doubles title). Later, he was able to establish himself on the challenger circuit, winning a US$25,000 event in Ecuador on red clay and then a US$50,000 event in Vietnam on hard court. This propelled his ranking to 11th in the United States and World # 127. In 2008, Zack added another professional tournament victory to his resume winning the Costa Mesa Tennis Futures.