kbassman,
I have tried this both ways and it works...thought you would like to know.
You have 2 alternatives:
1- If you like DLink as router, configure Zyxel WAN as Bridge, Encap=RFC1483, connect Zyxel LAN to DLink WAN, configure DLink WAN as PPPoE.
2- If you like Zyxel as router, connect Zyxel LAN to DLink LAN (DLink WAN empty), be sure DLink LAN IP is different from Zyxel LAN IP, disable DLink DHCP, if you want DHCP Server user Zyxel DHCP.
Enjoy