You probably have an AppleTalk Phase I versus Phase II issue. Most Hayes Interbridges are Phase I devices, while an unaltered Internet Router is Phase II. An "upgrade utility"--an INIT--comes with the Internet Router. Once installed in the System Folder of the router CPU, the INIT lets the Router pass Phase I packets. As a short-term workaround, you can install this to get up and running.
Due to the complexity of the network, we advise upgrading all devices to AppleTalk Phase II. With the zones and routers you mentioned, the Phase II protocols will be more efficient. Usually, this upgrade can be done through software. The Interbridge is the exception: it requires a ROM upgrade.