The directions I gave you were for resetting the Zyxel so you could use it as a access point on the other end of the house from the Comcast device. The comcast device will be untouched under this plan.
JUst make sure you set the Zyxel to a static address on the same subnet that the Comcast router is handing out. The comcast is [probably] on 192.168.1.1 so give the Zyxel an address of 192.168.1.2
As others have said, plug the ethernet cable into one of the 4 LAN ports on the back of the Zyxel NOT the WAN port. -- The difference between genius and stupidity is that genius has its limits.