I'm not familiar with this specific material at all but zbrush used to just use matcaps for everything so if that's still the case just look for a matcap material tutorial, copy that and feed it the appropriate matcap LUT
SkinShade4 is a "standard" material inside zbrush. If you open up the materials palette and expand the modifiers section you can check out all it's shader settings. It doesn't look like anything too complicated (just a slight increase in ambient contribution and blue tint in the specular from what I can tell). You could…