I don’t quite understand what you want to do. With zerotier there is no problem linking other home networks, that is, we can transparently ensure that any device connected to the zerotier network reaches any other device on a home network, even if it is not connected to zerotier, whether it is a local network or a remote network. In short, install zerotier on as many devices as you can (arm, rpi, pc, …).
In order for a device not connected to the zerotier network to reach a device on the zerotier network, we must be able to establish routing, and if you can modify the routes of this device, you will not have any problems installing zerotier either.
Although this article is already old and there are better ways to do things, you can start by reading this mini tutorial https://discourse.coreelec.org/t/coreelec-and-zerotier-a-good-couple