How to connect 2 ZyXEL Keenetic routers?

Question

Computer networks

Hello. I connected 2 routers by cable - mine and the neighbor's.
My router receives the main signal and gives the Internet to them.
Such a problem, the instructions say to insert my LAN into their LAN so that there is one network.
The network still appeared alone, I went into the neighbor's Wi-Fi - I went into the router, and hob, I'm in the settings of my router.
I don’t really like it, because they can wind up something and both of them will go astray.
I know that it is possible to divide the network into 2 links. But how? Can anyone suggest? I did not find examples of how to do this exactly on ZyXEL. I will be very grateful.
Routers:
My - ZyXEL Keenetic Start
Neighbor - ZyXEL Keenetic Omni

Answer 1

And if you plug the cable from your lan into the neighbor's wan and set up a connection with them via a static or dynamic ip, then they will be with the Internet and they won't get into your network ...

Answer 2

To prevent anyone from accessing the router, you need to change the password on it.