Allow a node to use internet traffic of another node

Im running a VPN server. Users connect with a protocol (TCP mostly, but can connect with UDP if necessary).
So users have to connect to a server in my country first, and the connect to a foreign server.
What I want to do is to establish a tunnel with Zerotier ( or anything else that works because most of the protocols are blocked here) between my country server and my foreign server and then send the traffic from my VPN server to that interface.
Sending traffic from my VPN server to an interface is the easy part because the VPN server can handle that.
What I have already done is created a network in Zerotier and connected both my servers to that network.
I can ping my country server from the foreign server and wise versa, but I can’t use the internet connection of the foreign server on my country server via the network interface Zerotier created.
I tested it using ping -I zxxxxx [google.com](http://google.com/) but it won’t ping.
Any idea how I can allow my country server to use my foreign server’s internet connection over this tunnel?
Both servers are SSH.
My country server is: 10.243.43.232 with public IP 1.3.5.7
My foreign server is: 10.243.116.97 with public IP 2.4.6.8

My VPN server can redirect the outgoing connection to 10.243.43.232 because it is assigned to an interface on my country server. I want all the redirected packets to the zerotier interface on my country server to get send to internet of my foreign server.