In fairness to Chalmers, from here:

I think that most arguments that use zombies can actually be rephrased in a zombie-free way, so that these arguments can be set aside if one prefers; but zombies at least provide a vivid and provocative illustration.

He does believe in the logical possibility of zombies (though I can't understand why) but does not feel that they are necessary to his position. You can certainly read his papers if you want to know anything more specific.