Zach is the director leading the audition that makes up A Chorus Line. He was originally portrayed on Broadway by Robert Lupone and largely modeled after director Michael Bennett.
No information is given on Zach's early life. It is only learned during his confrontations with Cassie that they used to live together and he started as a choreographer before working his way up to directing. Personality-wise he is authoritative, a perfectionist, a workoholic, and according to Cassie has a fear of intimacy and is always needing to prove himself.
His usual costume includes tan slacks, a collared shirt, and a sweater with a geometric design on it.
Zach and Larry demonstrate parts of the opening dance in "I Hope I Get It" and weed out the mass of auditioners to the final 16. Early on the audience learns he has worked with several of the dancers before, including Cassie. After the opener, he retreats to his desk that is normally located in the back of the theatre to conduct the interviews. He does not even leave the desk during his first confrontation with Cassie, only coming back onstage after hearing Paul's story to comfort him, and he remains there the rest of the show: demonstrating part of the "One" dance, having another confrontration with Cassie, helping Paul after his injury, inquiring what the auditioners would do if they couldn't dance anymore, and taking part in the Finale.
Zach was portrayed by Michael Douglas in the 1985 movie adapation of A Chorus Line. He does not dance at any time, leaving all the leg work to Larry. He is also more authoritative and confrontrational with his manner of interviewing, only softening after hearing Paul's story. Flashbacks of his relationship with Cassie indicate he has a dance studio in his loft.