I don't have ZBrush, so I can only give a couple of general suggestions. One, if you're exporting directly from the figure, make sure you only export the head (and not the tongue, too). Also make sure the "Weld Bodypart Seams" checkbox is NOT checked. As an alternative, you could import Dina's .obj file into Poser, spawn props with the group tool, and export the head body part from there. Also, I don't know about ZBrush, but some 3D apps will triangulate meshes, which will ruin the morph for sure. It might be something to check anyway.