By the pattern of the responses I would bet on the fact that Cisco Router 1 has not adequate static routes, since it responds only when traffic comes from its directly connected interfaces.
There also seems to be a mixup of the networks. Production LAN has 192.168.0.0/16 which overlaps with the Office LAN as well as the Labs Vlans.
Is there any kind of NAT at the Cisco?
Any kind of tunnel?
It would be much easier to enable dynamic routing, RIPv2 that is supported with ZS to announce at the Cisco routers your networks, as well as the default route. ZS would also learn the Production LAN and it’s state.