i am pretty new to it too (only been using it about 3 months) but i do know if you are using z_brush ridiculously high poly count are just par for the course... the good thing is that you can bring it back into maya without that high poly count. there are some tutorials out there that will show you how to bring you model back into maya and keep you original poly count without losing the detail you did in z_brush. just subdivide your model a few times (i usually keep mine around the 4th or 5th level...) and go from there. i am sure you are familiar with the different brushes and alphas in z_brush...combine a few and see what you get.

cupcakes,
whitney