Will the connection between these routers be wired or wireless? Depending on which you plan to use, you would want to configure the Netgear as either a repeater or for a roaming-type network with the ZyXel.
This Netgear router is not just old, it would be considered "ancient" by today's standards as it is only capable of 802.11g wireless mode. It also only has 10/100 Mbps Ethernet ports.
Using a router as wireless "extender" is not very efficient. You may get a stronger signal at the extender's location, but the overall bandwidth "speed" could be cut as much as half. As den.thed has mentioned it would be better to use a dedicated ZyXel extender than the Netgear that you are proposing.