The first thing to know about Zhuangzi is that it is a man and a book. We're only confident that whoever we call "Zhuangzi" wrote the first seven–"inner"--chapters of the book which bears his name, with a smattering of passages which that guy probably wrote too.
The second thing to know is that this book is really fucking good.
AC Graham and Brook Ziporyn have the best translations. Don't bother looking elsewhere. Ziporyn has the benefit of translating after Graham's groundbreaking work, and retains much of the literary quality of the original text, while Graham is precise and published an unabridged edition. But even if you pick Zip you need to read Graham's piece in Disputers of the Tao about Zhuangzi.