Zasa is a longtime member of the crew that had once been headed by Peter Clemenza. Following the retirement of Ritchie Nobilio, successor to Frank Pentangeli (Michael V. Gazzo) in The Godfather Part II, Zasa is awarded all the Corleone family business in New York with the approval of the Commission and Michael Corleone (Al Pacino). Zasa is feared and, to a certain degree, respected among his peers in the New York underworld for his business acumen and utter ruthlessness. However, his flamboyance and hunger for publicity earns Michael's displeasure, as it attracts unwanted public attention to his criminal past at a time when he is trying to restore his reputation. Michael especially disapproves of Zasa's eagerness to deal in the drug trade. Hence, Michael largely keeps him at arm's length.
In The Godfather Part III, Zasa first appears at a party honoring Michael, where he gets into an argument with Vincent Mancini-Corleone (Andy García), the illegitimate son of Michael's long-dead brother Sonny. Zasa calls Vincent a bastard in front of Michael, prompting the enraged young man to bite Zasa's ear. Zasa subsequently hires two assassins to kill Vincent, but Vincent quickly dispatches both of them.
Later in the film, Zasa is part of a plot to have Michael murdered during a meeting with all the various Dons in Atlantic City, New Jersey. During the meeting, Michael insults Zasa, prompting him to storm out; moments later, a helicopter containing gunmen hovers above the room and guns down nearly everyone inside. Michael escapes, but nearly every other Don attending the meeting is killed. Those who survive make deals with Zasa.
Several days later Vincent assassinates Zasa in Bensonhurst during a street festival. Vincent's men and Michael's personal assassin Al Neri (disguised as members of the church procession) kill Zasa's bodyguards, while Vincent (disguised as an NYPDMounted Patrol officer) shoots Zasa three times in the back while he tries to break into a locked store-front to escape.