Router on Router

Dear Experts,

I have nicely running NTL broadband shared over a wireless network using a D-Link DI-624+ wireless router. With the recent uprising of VoIP I decided to give it a whirl. I purchased another router with a built in VoIP adapter (Zoom V3) so that I could still use my normal house phones for both PSTN calls and VoIP calls. And I registered a sipgate account.

Ok, now the next step, is to get the Zoom router talking to the net.

I wired the Zoom router into a normal switch port of the D-Link router and disabled all WAN addresses and DHCP,NAT,DNS and Firewall settings on the Zoom router as the D-Link one should take care of it all. This all worked great. Except that I don't think the Zoom router is reaching the outside world. It's merely a switch now.

The D-Link is on 192.168.0.1, 255.255.255.0 and is also the DHCP server.
The Zoom router is on 192.168.0.120 (Reserverd IP from the D-Link Router) and 255.255.255.0, but with no DHCP,NAT or DNS.
The Zoom router's WAN settings are Static IP 0.0.0.0 and Gateway 0.0.0.0.

I plugged a machine into a switch port on the Zoom router and configured it's IP to 192.168.0.125, 255.255.255.0, and a gateway and DNS of 192.168.0.120. I figured that this would determine if the Zoom router is in fact getting to the internet. I then used this machine to try and open up google, and it failed.

I think one solution is to swap the two routers over but I am reluctant to do this incase I screw up my entire network.

Basically I need to get the Zoom router to connect to the internet going through the D-Link router.
So there are two parts, how do I do this and how do I check that it is working?

Any help is sooooo greatly appreciated as I am totally knackered with this, and as its 3:47am I have reached the IT man's wits end.
Please experts, help me!!!!

A million thanks in advance.
Riyaz.