You might be able to tell I don’t come here very often…
I have run Zeroshell in both VMWare (server on Windows and ESXi), and also in Virtualbox (windows and solaris). It works just fine.
To get Xen to work, you need the Paravirtualization support, which means a proc with Virtualization extensions. Then you should be able to run it fine there, as well.
This should technically also mean that it will run on any other of the full virtualization software packages. The question is performance without being able to install the guest extensions. The VM performance will suffer a little, but Zeroshell does not have that high of requirements, so any modern machine will handle it well even under full virtualization without processor support.