[1] He originally matriculated at Notre Dame, but suffered from a change in the offensive game plan when Bob Davie replaced Lou Holtz, who had recruited him.
[2] By the time he was a sophomore during the 1994–95 school year, he was as well known as one of the best football prospects in the Chicago metropolitan area as he was as a scholar who ranked first in his class of 925 students.
[10][11] Although he was a standout in football, he earned a Chicago Tribune prep athlete of the week award for his basketball performance both as a junior and as a senior.
[17] That season, he again led Sandburg to the Class 6A football playoffs,[18] but the team only went 6–4 as he endured injuries and an inexperienced offensive line.
[20][21] Although head coach Lou Holtz left Notre Dame following the 1996 season, Kustok remained committed to his replacement Bob Davie even though Ron Powlus decided not to enter the 1997 NFL draft.
[26] Kustok, like Powlus before him, was more of a drop back passer and suddenly found himself fourth on the depth chart at the beginning of the 1998 Notre Dame season.
[38][39] Kustok made his debut after Northwestern fell behind Minnesota 14–0 in the game and head coach Randy Walker removed starter Nick Kreinbrink.
[42][43] He was a 2001 finalist for the Johnny Unitas Golden Arm Award along with Joey Harrington, David Carr, Eric Crouch and Kurt Kittner.
His wife Nicole (née Kuznia) was named Minnesota's 1999 Junior Miss and was also a cross country runner at Northwestern.
In 2014, Zak graduated the University of Notre Dame with an M.B.A.[citation needed] On September 29, 2010, Kustok's mother was shot and killed; his father Allan was accused of the homicide.