Managed routes, limit which clients should talk to each other

Hi,

I have a setup where multiple remote boilers connect to zerotier, and it works flawlessly when i use the mobile 4G connection in the Router/Modem, but sometimes the customers want us to use their lan to connect to the internet which sometimes means that i get issues with the routing, so normally i setup a managed route like this:

Boiler 1
10.0.24.0/24
via 172.XXX.XXX.77

And that works, the problem right know is that the customer has in their network a 192.168.1.0/24 network

And i have in zerotier a boiler 2 with this managed route:
192.168.1.0/24
via 172.XXX.XXX.55

So this means that my zerotier instance tries to route the internal traffic on the customers network out trough the modem.

Have i gone about this all wrong?