This is the progression; I started with a base mesh female that I had previously made, then did a quick concept sculpt using a combination of dynamesh and clay / clay buildup / smooth trim border / standard / move / zspheres / trim dynamic and hpolish brushes:

This is about where I left off in the loose concept sculpting phase (the body anyway), then I went through and refined each piece. I usually have three refinement phases, starting with the quick loose concept sculpt (hpolish, pinch, trim dynamic to refine shapes), then breaking pieces apart that make sense (mask, hidept, split, re-dynamesh, then refine each piece quickly. Last, I’ll rebuild those pieces using the topology brush / zspheres / zremesh, then hide / crease borders, subdivide, uncrease / subdivide to get a nice bevel. What this does is provide me with basic forms quickly that have super smooth surfaces, then I dynamesh them at a high resolution and keep refining / detailing / combining / subtracting forms from there, or slicing / group dynameshing / autogroups / smooth to make really clean cuts between forms:

Smaller, specific pieces I’ll make using primitives / initialize / transpose modeling, or use shadowbox and clip brushes to refine, then decimate them and add them to my insert mesh library. The different wires and tubes are default insert mesh curve brushes in Zbrush:

I have the helmet split so that if I want to eventually animate it open, I can add some padding, respirator, and / or some other things stuffed in there:
