Zima began her career at the age of 23 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 soon to be released movies Dimples, Looking for Sunday, Once in a Very Blue Moon and Legacy.

In 2007, Zima played Mia Lewis, a sexually precocious and worldly 16-year old, on the series Californication. The part, which included a sex scene with David Duchovny, stood in sharp contrast to her previous television roles.