If you just want a bare bones free CLI-based hypervisor that also can do ZFS, check out SmartOS:
Home - SmartOS Documentation - SmartOS Wiki
There's a lot to take in but basically it's OpenSolaris, boots off thumb drive, uses ZFS as base file system, can do KVM virtual machines, and also lightweight vm's (look into LX zones).
I love it for my home lab.
but why go into this extremes?
if you want a Hypervisor that supports ZFS Proxmox is a very good candidate nowadays.
not sure about v5 yet.
but Proxmox VE v4.4 works well as far as I can say. I have been running it in my test config for a bit.
Support for ZFS out of the box. it even supports installing and running from ZFS raid setup.
installer options are ZFS RAID-1, raidZ maybe more but I am not into anything but raid-1 for OS/boot so stopped right there.
supports BTRFS as well even though CLI only (more point for me as I do want BTRFS support)
nice and very usable WebUI. why go only for CLI when you can have other options.
mostly standard KVM support. LXI support
NFS/SAMBA support as well as GlusterFS and others. all native and built in.
uses standard Debian kernel so you can install and use other software if needed.
supports HA clustering and even no shared storage clustering.
seams like a better option IMHO.