Ok....from first glance it seems that 1, the mesh in Zbrush needs to be much more subdivided before you export a map from it. 2, it seems that you have exported a normal map, or the wrong possible format. I'm not sure. But you're certainly on the money..something's whacked.

If an imported object is not polygon heavy enough in Vue, polygons will start to pop. However, Vue's native primitives can handle the toughest displacement. Not so with imports. Wish it wasn't so.

I will break out my Zbrush and investigate further....

M