Yes, I don't have a Ross crossover, but I have crossovers between my loops and go back and forth between loops all the time. Not a problem.
The only time you could have a problem is when using two separate transformers for each loop. In that case both would have to be in phase. Usually a more common problem with older transformers having non-polarized plugs, like the old ZWs and other postwar stuff. You should not have a problem using two handles of a Z4000 as they will already be in phase.
