Zbrush doesn not render soft normals in viewport. Try using BPR render with soft normals turned on to see what it actually will look like. Zremesher isnt there to fix facetting, it can with enough density, but you might as well just subdivide your mesh once more.
You need low poly model for video games . As well as for animation too . The one hi res surface could be baked as normal map or displacement . It's not only games related actually . Nobody animates anything made of millions of polys . You can use any retopology tool if you don't like Zremesher. Blender,3d max or MAya too…