In 2012 Zimmerman was relied upon by Northern Illinois to be the top offensive option for the team and did not disappoint. In 51 starts for the team this year he hit .267 with 29 RBIs and six home runs. Zimmerman burst out onto the scene of college baseball in 2011 with Northern Illinois, recording a .326 average with 11 home runs and 47 RBIs. The breakout year earned him First-Team Freshmen All-American honors and First-Team All-Mid-American Conference, along with being named MAC conference Freshmen of the Year. During his prep career, Zimmerman was twice named All-Conference and was chosen to the All-State team his senior year in 2010. His high school team won a regional championship in 2009.