Hi Chakib, do you use Zbrush for Z-Remesher to optimize polycount ?
I've recently incorporated one more step with Zbrush R6 to get rid of some imperfections from MD and optimaze bit further, the new Q-Remesher. It retopologises the mesh into super clean quads, efficiently smoothing all errors from MD, and then I get back the MD UVs using 3dsMax "Projection" modifier (it's just 2 clicks !). Then if necessary, I use Z-Remesher. Using this technique, you can then sculpt additional detail in Zbrush ( I do so using SurfaceMimic e-shops displacement maps).
It takes few more minutes but brings out tons of new opportunities.