The very basics of Zbrush. Navigation, creating PM3ds, Brush selection, Brush size and intensity, masks, mirror and weld and dynamesh.
If you want to see a sculpt from beginning to end check out my playlist here: https://youtu.be/foi6ANYd0WM
ZBHO Room: https://goo.gl/qb4Lpv
ZBHO CG Club: https://goo.gl/3CsMWW