Zbrush doesnt have smooth shading in the viewport, so these will not pop the same way as in max. This is why I never decimate You could probably use bpr render to see if you make this visible in zbrush
Just adding my .02's.: Yes its a weird thing that happens perhaps from inflate useage? I do not decimate either, i didn't decimate because i hated the ugly baked normals look i get from decimated meshes. They, Yes you have to pay attention to the levels you are creating and can't just go click happy to get the smoothest…