The Hyrlo probably has a hot left and right and cold common ground audio connection, yes. And sure, the Cockpit seems like it would be L+gnd and R+gnd...but what if it's not? Also, what if one module likes to see something like line-level at its expansion, but the other sends synth-level? Or if there's a big impedance mismatch? That'll sound quite awful.
Best thing you can do, unless you're working with either kit builds that you know the signal paths/levels on, or both companies say "yep, and this is how you do it...", just don't. Even if it doesn't result in catastrophic failure, it's still best left in the 'don't mess' category.