To create displacement maps from zBrush for the Daz figures, you first need to prepare the figure the same as you would for painting, as the figures have multiple UV maps and zbrush can handle only one UV map at a time.  If you look at my tutorial on painting Daz figures, the first part tells you how to prepare a figure so that the UV maps/material regions are easily selected in zBrush so that texture or displacement maps may be exported. Once you have your figure prepared and saved, you can import it into zbrush for displacement creation.

How to mask eyes so you can morph the head mesh around them in zBrush 3:

The head, left eye and right eye are separate groups when you import into zbrush. You can mask the eyes by selecting them. The combination of key strokes to do this may seem confusing at first, but it is handy to know how to show and hide different mesh groups.