This is fairly simple to do.
On Zeroshell 1 create the following Static Route:
Destination: 192.168.2.0
Netmask: 255.255.255.0
Type: Gateway
Gateway: 192.168.254.2
Metric: 0
And on Zeroshell 2:
Destination: 192.168.1.0
Netmask: 255.255.255.0
Type: Gateway
Gateway: 192.168.254.1
Metric: 0
