When I was creating the model, on many occasions, the mesh would become too stretched or have unnecessary holes created when modelling. It took a bit to figure out how to fix it, but with some online tutorials and continuing to work on it, the issues slowly got resolved, and I was able to do a few more intricate details through the whole head.
Alter Species - Alien Head Model
An alien concept I did while first starting in ZBrush I named "Alter." (The name is random, so don't think too much about it). This helped develop my fundamentals about the program with various brushes and techniques.