The easiest way to use the Z over ssh on another machine is to issue "xinit" from the command-line on the other computer, then type "ssh -l username -Y ip.of.zaurus", enter your password etc., and then type startx. This should provide the full Z desktop over ssh. You need to enable X forwarding in /etc/ssh/sshd_config on the Z for this to work.
Using full desktop environments from other computers on the Z is more difficult since xinit does not work (at least for me). I haven't really played with it much, but there may be a way with a .xinitrc file that only opens an xterm.