Whenever I've heard it pronounced, it has been ZO-ee, like the regualr Zoe. I watched (on Special Features of a DVD) and interview of a movie she was in, and all of her other cast members pronounced it ZO-ee.
Don't worry, you're not alone. I wasn't sure how it was pronounced until I heard people say her name before, either!
We love you Copper! 6/1/91 - 6/16/06 Matthew Craig 'Matt' 1/21/1977 - 7/11/2006