But it is as a director that Zaks has become better known. His first New York show was Christopher Durang's "Beyond Therapy" (1981). A year later, he garnered praise and had a big success with the double bill of Durang's "Sister Mary Ignatius Explains It All For You" and "The Actor's Nightmare". He has specialized in darkly humorous, wacky, almost vaudeville-style comedies and musical revivals, winning Tony Awards for his staging of John Guare's "The House of Blue Leaves" (1986), Ken Ludwig's farcical "Lend Me a Tenor" (1989), Guare's "Six Degrees of Separation" (1991) and an acclaimed revival of the Frank Loesser-Abe Burrows-Jo Swerling classic "Guys and Dolls" (1992). A font of energy, Zaks has also directed Stephen Sondheim's "Assassins" (1990), Neil Simon's "Laughter on the 23rd Floor" (1994), shaped the revue "Smokey Joe's Cafe" (1995), a popular revival of Sondheim's "A Funny Thing Happened on the Way to the Forum" (1996) and many other shows, hits and flops alike. He has won particular praise for his handling of actors and many have earned awards and/or some of the best reviews of their careers in one of his productions. Among them are John Mahoney and Swoosie Kurtz ("House of Blue Leaves"), Stockard Channing ("Six Degrees of Separation"), Philip Bosco ("Lend Me a Tenor") and Patti LuPone ("Anything Goes"). He has directed Nathan Lane to acclaim in three productions, "Guys and Dolls", "Laughter on the 23rd Floor" and "Forum", which earned a Tony for the actor.

In 1996, Zaks' career took a sharply different turn as he directed his first feature film. Based on Scott McPherson's play, the warm comedy-drama "Marvin's Room" starred Meryl Streep and Diane Keaton as long-estranged sisters who are reunited when one is diagnosed with leukemia. The film also boasted a strong supporting cast including Robert De Niro, Leonardo DiCaprio, Hume Cronyn and Gwen Verdon.