I tend to do this often too, but it looks like you're overworking your mesh. If you're using zbrush as a fine detail tool then that's fine, but i'd opt for a less specific mesh to give you more freedom in zb.

(BTW, if you are going that route especially, one thing you may notice is that zbrush will 'shrink' your model as you subdivide. This will cause issues when you take it back into maya. After importing the .obj, just store a morph target first, subdivide a couple times, step back down and apply the morph target again to fix it.)