Dont know if youve finished with the zbrush phase but, re: the smoothing problem...there is a way you can go into the modifiers of the smooth brush and edit it to make it less destructive. But what I think is a better solution is to get into the clay brushes, particularly clay tubes. These react much friendlier to smoothing,holding their shape much better. It looks like you are using the standard brush as your weapon of choice. I have all but given up on ever using the standard brush precisely because it crumbles so easy under smoothing.https://www.ravage3d.com/images/Game/Ada_2_1.jpg
Here is the start of Zbrush work. Is there any way to stop the face from scrinking so much when smoothed.