How to open a port through 2 routers?

Question

network hardware

There are 2 routers in the apartment, one ZTE in the corridor (installed from the provider), the second TL-WR841ND in the room (lan cables go to computers from it).
When I plug out the cable that goes from the first router to the second one, and connect it directly to the PC, the ports open.

I made a reservation for the IP IP mac address 192.168.0.111, then opened the ports for this IP - everything works.
BUT, as soon as the cable is returned from the router to the router, and from the second one to the PC - nothing, although I did the same operation in the settings of the second router (I gave a permanent address to my PC and opened ports), and in the first I changed the PC's poppy address to MAC address of the router. In fact, it turned out that I opened ports for another router, and in the router I opened ports for the PC. But for some reason it doesn't work like that.

Answer 1

Another option:
1) change the LAN network on the second router to be different from the network of the first (for example, on the first 192.168.1.0, on the second 192.168.2.0).
2) on the second router, set the WAN Static IP from the network of the first router (for example, 192.168.1.10) in the WAN settings and disable NAT.
3) on the first router, add a route to the network of the second router through its address, for example, 192.168.2.0 through 192.168.1.10.
4) all NAT settings and port forwarding are done on the first router, even if the computer is connected to the second one.
There will probably be a problem with the fact that the router will only accept addresses from its own subnet as a port forwarding destination (although it will nat addresses of both subnets and in theory can forward ports to any subnet, this is only a limitation of the user interface). In this case, you can play around with the developer mode in the browser and change the HTTP request parameters.