How to move the /Users to an encrypted ZFS drive?
With reference to the linked question (the comment there from the opening poster here) …

In brief: 

Unlocking the Core Storage LV, importing the ZFS pool and mounting the ZFS file system

I know of no way to force Mountain Lion to use the Core Storage volume encryption key (VEK) in a way that will allow the ZFS pool and file system (based on the Core Storage logical volume (LV)) to import and mount – automatically – in a way that is comparable to the FileVault 2 experience. 

In other words: 


the current operating system seems to require manual intervention by a different user whose home does not use the combination of Core Storage and ZFS


… part of that bullet point might provoke, from someone else, a more thoughtful approach to intervention; a better answer to part of the question!

ZFS for /Users

With or without encryption: 


if you plan to use ZFS for /Users you should first have an administrative user whose home is not in that area.


Consider at least: 


safe boot of the operating system, which might be required when least expected/desired; and the related limitations of current implementations of ZFS for OS X (example: safe boot and ZEVO Community Edition 1.1.1).


ZFS for home directories with Mountain Lion, or words to that effect, could be a good separate question.