Zimmerman grew up in
Great Neck, New York, attended
Great Neck North High School, and was coached by his uncle Bob Litwin. He played varsity tennis for
Harvard University and was a member of four successive
Ivy League championship winning teams, from 1989 to 1992. In both 1991 and 1992 he earned Ivy League Player of the Year and
ITA All-American honors. As a junior, he was ranked as high as seventh in the U.S. and No. 1 in the East. Zimmerman reached a best singles world ranking of 349 on the professional tour. He featured mostly at satellite and ATP Challenger level, but had a quarter-final appearance in doubles at an
ATP Tour tournament in
Bordeaux in 1994. ==Personal life==