Zapata was a Staff attorney of Pima County Legal Aid Society, Arizona from 1973 to 1974.

He was an Assistant adjunct professor, University of Arizona College of Law from 1988 to 1990.

He was nominated by President Bill Clinton on March 29, 1996, to a seat vacated by Judge Richard Mansfield Bilby.

He was confirmed by the United States Senate on July 31, 1996, and received his commission on August 1, 1996.

In 2013, Zapata received the Public Service Award from the University of Arizona Alumni Association[1]