For those who stumble across a similar problem. I finally went and hooked my LAN on my ZS computer directly to my MacPro for testing. Turned off the dhcp server on ZS and turned it back on and it started serving IP to my Mac. Plugged it back into the LAN switch and everything is working. I have no idea what fixed it other than a stale cache somewhere.
BTW, on ZS the DHCP log still says another DHCP server is running but it is handing out IP regardless.