It depends on what you're modeling, but in most cases you'll want to retopologize then export for animation. Of course, z3 is equipped with the retopo functionality. Remember, normal or disp maps are your friends and it's in this capacity which Z excels.
Insofar as mesh smoothing is concerned, you can always average the verts in your target animation package without adding geometry. If you're using Maya, there's a downloadable script that subds your geometry without adding density - I can't think of it atm, but search around and you'll find it. I'm pretty sure CPS has it, too.