I’ve noticed that whenever I make or add edge loops to a base mesh/part/subtool in 3 ds max even when divided to a million polygons in zbrush it doesn’t seem to hold detail. I am no max guru, but is there anything that needs to be done to a mesh before sending it to zbrush?
It really just comes down to your edgeflow, and the density of the mesh. 1 million verts might not be a lot if a good chunk gets wasted in an area that has smaller polygons, and the rest has to be spread out over a larger surface.
You could try creasing the edge in 3ds Max and subdividing it once or twice before sending to ZBrush.