On the topic of ZBrush, thinkcooper mentioned in another thread that they were working on GoZ integration... in case anyone missed that too...

But, subtle tweaks using the V4 base expressions morphs can be pretty effective too, in a lot of cases, I reckon...

...I think that a lot of facial asymmetry in a person is maybe down to muscular / neurological factors... so using the expressions morphs is perhaps not inappropriate relative to that.

;-)