Normally when you use the remote controller feature, you have one controller dedicated as master controller, the other remote controller. That way you can map all zones on the remote controller to virtual zones on the master controller. For example, in your case, you can set your master controller to have a total of 8+24=32 zones, even if it only has 8 physical zones. Then you defines its zones 9 to 32 as remote zones on the remote controller. This way, all zones are operated from the master controller, and since the pump zones is also on the master controller, when any zones opens, the pump zone opens as well.
The way you have set up is also fine. Yes, it seems a bit awkward to carry the password and explicit duration. But that’s mainly because you are not use the remote zone feature, which would have managed the password and duration implicitly (by requiring the master and remote controllers have the same password, and the duration is sent automatically when a zone opens).
Another way, which we haven’t tested rigirously but should also work in your case, is to define your second OPSi’s master as a remote station, which maps to the first controller’s phantom master zone. The UI would set the first controller in remote extension mode when you set this up, but later you can access the first controller and simply remove it from remote extension mode. The good thing about this approach is that since it uses remote zone feature, password and duration are sent automatically. The downside is that if the first controller is independently running the master zone, while the second controller is sending a command to do something different, it may lead to master zone status that’s different from what you expected.