I have a Raspberry Pi Zero W V1.1, SD Ultra 32GB card with 2018-04-18-raspbian-stretch.img installed. A USB powered hub (with its own 5V 2A power supply) is connected to the Pi Zero W via an OTG USB cable.
I connected a Huawei E3272 USB modem to the USB hub and through it I am able to connect the Pi Zero W to the Internet. The Pi Zero W wireless is OFF.
I then connected an RD9700 (a.k.a DM9601) type USB 2.0 Ethernet adapter to the USB hub. Using an Ethernet cable, I connected a DD-WRT wireless router to the Pi0w via the Ethernet adapter. This was done using one of the LAN Ethernet ports (not the WLAN port) on the router. I was then able to access the router's HTML GUI on the Pi Zero W.
I had previously checked that the router's WLAN port was working by trying it with another modem.
With the USB modem, Ethernet adapter, and router all communicating with the Pi Zero W, I then switched the Ethernet cable from the router's LAN port to the router's WLAN (Internet) port, hoping the Pi Zero W would feed its Internet connection to the router.
Alas, no Internet from the Pi Zero W to the router.
In effect, I want to set up the Pi Zero W as a WiFi hot-spot that also allows Ethernet connection to the Internet. How do I get the Pi Zero W to feed its Internet access to the router via the Ethernet cable?