Polygons are polygons; regardless of the program. ZBrush doesn't average the vertex normals, but if you import the mesh into another program there shouldn't be any visual difference.
Yes, I've heard that the graphite tools could be used towards retopology, it's nice to hear they are actually usable. I will certainly give them a try. This is a very interesting idea, I wonder how well it could work as the lowest level of the ZModeler mesh tends to be a little blocky and ugly, as opposed to counterparts…
Also the result of any mesh subdivided 5 times :P ZRemesher isn't really aimed at retoplogizing hard surface models, at least not in a way that is specifically geared for games (the same could technically be said about characters, but organic shapes tend to be more forgivable). It's more a less a way to take a hardsurface…