How to access Zyxel VMG3006-D70A Modem Page? (RPI4B)

Hello, i am using a RaspberryPi 4B which i connected it via a USB to ethernet adapter on eth1.

I already looked at this page, which only shows how this will work with a wan interface:
https://openwrt.org/docs/guide-user/network/wan/access.modem.through.nat

Now my question is how to setup it with my adapter.

The same way.

What you mean the same way? i don't have @wan in the interfaces?
grafik