The zsh comes with extensive documentation, but often people have trouble when starting to use the shell, because the documentation is too huge.
So, zsh-beginners may want to start off in this order:
After those you may want to check out this wiki (which is mentioned in the manual, that's why I consider it somewhat official).
If you've closely read the above, you should be able to use the zsh pretty well already. But of course there are things that are missing, but which are in the zsh manual (which is a great reference). In newer versions of the manual there's a page called zshroadmap(1), which helps a lot when you try to get an overview of the various pages).
There is an online version of the manual:
Older docs, removed from the above list because recently people have been annoyed that some of the features presented in the material works differently in recent versions of the shell than presented in herein:
- Older Intro by Paul Falstad - the original creator of the z-shell; it's pretty old, but most of the information is still valid. You may savely skip this, if the you read pws' Guide.