As far as I know, to fully utilize the mocap data for the face it would take a good deal of scripting and you would have to rig the character's face correctly. There may be a plug-in that could help you out but I am not currently aware of one.
As far as Z-brush goes, bring in a lower resolution model into Z-brush and paint in your detail. It is best to use on full mesh and not separate pieces.
I would rig the low poly mesh in Max using skin or physique and make sure that it deforms the way you want. You may want to use the skinmorph modifier on top of the skin modfier to make sure the deformations are correct.
Once this is done, merge in the detailed, hihger mesh (z-brush) model. It should line up perfectly with your lower poly model. At this point, simply use the skin wrap modifier on the higher mesh. You can tweak the control points to your liking to make sure that the mesh deforms the way you want. If there are still problems, you can easily convert the skin wrap to skin and tweak it from there.