Connecting devices without ZeroTier

Hi all,
I have 2 network devices (say home H and office O) connected to the same ZT network. Now, both are connected to a respective LAN, home-LAN and office-LAN and are the connecting nodes between the Internet/ZT and the relative LAN, as they also provide access to the Internet. I can’t install ZT on the devices in the 2 LANs -besides H and O- and I can’t register their MAC addresses on ZT. Is it possible, and if so how, so SSH from a device in home-LAN to a device in office-LAN? I am administrator and I can change anything needed. Ideally this should work both with static and dynamic IP addresses.
In other words, how do I make the devices in office-LAN “visible” to the devices in home-LAN, and vice versa? And what do I need to enable? Is forwarding enough? Do I need iptables?

If your routers can install a zerotier package (MikroTik, OpenWRT) the easiest method is to have them be members of a zerotier network that has routes to the local subnets on each site. Then you don’t need to install anything on the computers themselves and it becomes a site-to-site VPN connection. If this is the only use case (no external remote access etc.) you might be better served with something like Wireguard or an old school OpenVPN connection.

If you also have roaming users, then Zerotier becomes more interesting since you can use the single zerotier network to give access to both sites from any network connection.