Thanks for that head's up. It turns out that it *somewhat* works.
Officially, it works well at this point and it does install both aggregate routes in the device's routing table. The really weird thing is that officially from ZebOS' point of view, only 0.0.0.0/1 is accepted and installed, even though both routers send 0.0.0.0/1 and 128.0.0.0/1, yet in the device's routing table, I see 0.0.0.0/0 with both routers as a destination, and it can properly communicate with IPs in the upper /1 range.
For some reason, it doesn't want to accept the 128.0.0.0/1 route, as when it's the only route advertised by one of our routers, it does't install anything. I don't understand why or how at this point, but that's another troubleshooting issue that I'm currently trying to figure out.
I have to figure this out, as I'd rather not have a weird state and it's definitely the most efficient solution so far.
Thanks a lot for it!