There are a number of tutorials and courses in LinkedIn Learning that cover aspects of Pixologic ZBrush. Some recommended resources to consider are below. In order to access these tutorials, you must first login to LinkedIn Learning and search for them by name.
ZBrush 2018 Essential Training
ZBrush: Product Prototyping Techniques
ZBrush: Tips + Tricks
ZBrush 4 Essential Training
Sculpt Cloth in ZBrush
ZBrush: Sculpting Portraits
Sculpting a Creature with ZBrush and Photoshop
ZBrush: Stylized Sculpting
ZBrush: Rendering