I made this characters for a course and it was pretty much fun, although it took almost 2 months to finish the course. It was that much time, because everything is in real time, no timelapse or speedups and the course is 36 hours of content. Starting from sphere and using only Zbrush and nothing outside of it.
The concept can be found here: https://www.artstation.com/artwork/nQYWX9
I think whoever has the patience to watch it will benefit a lot from it . I have one very important advice for the people willing to learn how to do this - do your own model with the videos. Watch and model at the same time. Having two monitors will help, of course . But modelling parallel to wathcing will boost your skill immensely. Here is a link to the tutorial if you like it: https://www.udemy.com/course/orc-rider-and-bull-creature-creation-in-zbrush/?couponCode=NIKOLAY05-YOUTUBE