zBrush is pretty good, but it isn't exactly a modeller. It is more of a sculpting and texturing tool really, works best if you model a low detail mesh in silo or hexagon or something, then import it into zBrush for details and textures/bumps/displacement maps. These maps are then applied to the original low rez mesh with displacement for the details so it renders and animates fast.

Not saying you cant model something from scratch in it but if you do, you will end up with a very dense, multi million poly mesh that is hard to use in poser (or most other apps)