In ZBrush tools can’t be retopologized without destroying existing 3D layers. In Blender, objects can be retopologized and existing Shape keys will be altered accordingly. The altered base object and its shape keys can then be reimported into ZBrush. The conversion is tedious work.
Figurative art is all about observation. Looking at the work of other artists helps to improve an artist’s technique. These are the artists who inspire me to be better. I learn just by looking at their work and some of them have videos detailing their technique.