https://www.youtube.com/playlist?list=PLpoXxlr0idMlwAWdx1BkTwHZfhuIdppDI
This free tutorial series covers the complete process of creating organic hard surface geometry with Zbrush. It includes detailed examples of many tools and techniques available in Zbrush, including Spot Light, sculpting basics, Dynamesh, retopology, creasing and Dynamic Subdivision, Zmodeler, creating and using Insert Multi Mesh brushes, using assets from the Artstation Marketplace, Zremesher, and Live Boolean.
Part 1 covers Zmodeler, Dynamesh, Insert Mesh Brush, Poly Groups, Live Boolean, Zremesher, creating geometry from alphas, working with Curves, and creating clean high poly geo with retopology. It is available here: https://www.youtube.com/playlist?list=PLpoXxlr0idMkF5l8uSrdFJiWNXLE-joUn