In an interview with "action-adenture movies" website, Zooey talked a bit about Hitchhikers. No secret revealed ("I’m not sure if I’m supposed to be talking about it because they were very protective" she says during the interview), but it's a nice chat where Zooey said what she has to say about Hitchhikers : "It was great, it was so much fun to make that movie".
She recalls that they "had these seven foot tall alien Vogon puppets. They built four different alien planets, the Heart of Gold set, like the most amazing sets and all the actors were great".
We even learn a little about trillian's look in the movie : "I have a couple different costumes but the main one is this sort of aqua one piece suit, sort of like a karate one piece. It’s really cool".
When asked if the movie will be close to the book, she replies yes. "Most everything that was changed was Douglas Adams’ idea to begin with".
Interesting fact, she reveals that all main actors signed "sequel parts of the contract". Even if it's a bit early to say if there will be a sequel (it will depend on the Hitchhiker's movie success), everybody think of course about a possible sequel.
She also says that, although it's "a big movie", probably the biggest movie budget she's worked on, "the interesting thing about Hitchhiker’s is it’s also a character piece. It’s just within the context of all this fantasy".