Alrighty then,
Simple question people, I am thinking of getting started with Zbrush but there are a few pestering, irritating things that keep on bugging me, so I was wondering if anyone would be kind enough to help me out here. I know that sketching is essential for Zbrush(if you want to get really good at it anyway) and while my sketching skills aren’t anywhere near good or even mediocre I am slowly working on them, but what about anatomy? Do you have to know anatomy as such to get started with Zbrush?
I would, in the beginning at least, start with modelling just game assets for environments(hard surface modelling more or less), I am relearning Max(9 months without a system, I have forgotten most if not all). So my ultimate question apart from what I asked above is that are there any prerequisites for starting out with zbrush as such? Also what are some good videos for the absolute beginner?
-Cheers 
Sketching is important for creating art in general but it doesn’t necessarily translate to sculpting in zbrush.
Anatomy is very important for creating believable biological characters but it is something you can fake by copying photos until you gain a good understanding.
The only prerequisite I would say is to buy a wacom tablet or at least a cheap knockoff. It is not essential but it makes a huge difference.
The rest is just to practice and always have reference material.
As for tutorials there are some good ones in the zclassroom on zbrushes website and 3dtotal have a good range of free tutorials. If you are willing to pay then gnomon dvds are really good.
I would highly recommend getting “Introducing ZBrush” by Eric Keller. I have the Third Ed., which is working fine for 4R5 (I haven’t gotten much past the basics). In about two weeks, I’ve already learned a majority of the fundamentals of ZBrush, or at least enough to follow industry professionals when they start talking in ZBrush jargon. 
If you are looking for some helper material for sketching people and animals, I would recommend looking at “Cartooning For the Beginner” by Christopher Hart. He’s a great artist and really breaks down how to build up a character. If you’re into Manga or Anime, he’s got a lot of great books on that stuff, too. I find that, in general, he’s the best resource for beginning artists, since he breaks down EVERYTHING into small, easy-to-learn pieces.
And, if you’re looking for an inexpensive Wacom Tablet, I would highly recommend one of the Bamboo Splash tablets. They’re only about $80. While the drawing area is small, I find that my 6" x 4" old Bamboo Fun is fine for working with ZBrush.
Sketching is always a good thing, but I’ve found that actually working in clay can do wonders for your technique, too. You might consider taking a Ceramics/Sculpture class, somewhere. Or even just buy some Sculpey clay and start experimenting. I think that the most important thing is to just understand 3D space.