I have connected my Zyxel VMG8623 modem/router to the ER605 WAN input through wifi, using a Tenda Wifi/router that is been setup as Station(Client) acting as a "Wireless Adapter". I had to do so, because in my area we have a lot of thunderstorms that are passing through the telephon cables, destroying any equipment that is cable conneted (and I have a lot of them). 

The problem is that port forwarding is not working, while any other internet connection is perfect. The Zyxel Lan is 192.198.2.x (1 for Zyxel, 2 for ER605 and 241 for Tenda), while the "internal" LAN (created by ER605) is 192.168.1.x. I have setup in the Zyxel a port forwarding to see the Tenda from the web (51080 to 192.168.2.241:80) and I can access it. But I can't do anything to see the devices in my LAN, not even the ER605. I have set to the Zyxel a forwarding for the ER605 (11080 to 192.168.2.2:80) but there is no access from the web. If I use the 192.168.2.2 as destination from a devive in the "internal" LAN, I can access the login screen. 

I also have set a port forwarding at ER605 for a PC 192.168.1.4, but I can't access it. I tried to forward it also in Zyxel using as target the ER605 (meaning destination 192.168.2.2) but nothing happened.

So my question is if anyone can understand what I am doing wrong.

Thanks in advance for any help