Zima was born in New Haven, Connecticut, to Marie and Dennis Zima. She has two younger sisters, Vanessa and Yvonne, both of whom are also actresses. Her surname means "winter" in Polish (also in Czech, Slovak, Croatian, Russian, Serbian, Ukrainian and other) and comes from her paternal grandfather who was from Poland.

Zima began her career at the age of 24 months when she was chosen as a toddler to appear in a television commercial for Downy fabric softener. She played the role of Grace Sheffield on the television show The Nanny for six years. Zima has become known for her work in films such as The Hand That Rocks the Cradle and having most recently appeared in the Hilary Duff film A Cinderella Story and the soon to be released films: Dimples, Looking for Sunday, Once in a Very Blue Moon and Legacy alongside Hillary Duff's sister Haylie Duff.

In 2007, Zima played Mia Cross, a sexually precocious and worldly 16-year old, on the series Californication. Zima returned for a second season of Californication in 2008 reprising her role as bratty 17-year-old Mia. In promotion of Mia's book, Fucking and Punching, Zima starred in several Californication webisodes that are featured on YouTube. In 2009, Zima joined the cast of Heroes as Gretchen, Claire Bennet's quirky bisexual roommate and tentative love interest.

She stars as Jill in the 2009 release The Collector.

She was nominated three times for a YoungStar Award at the YoungStar Awards, in 1995, 1997 and 1999 all of them for Best Performance by a Young Actress in a Comedy TV Series for The Nanny (1993).

She was also nominated thirteen times for a Young Artist Award at the Young Artist Awards: