If it crosses the main and does not in any other way interact with it, electrically, there is no need to phase them. Phasing is a method to create a common return for two or more separate, (similar or dissimilar) electrical sources.
That said, because it's so easy to do, go ahead and phase them. Unless there's something about the output of a Z1000 that would not like it. Since I wouldn't know a Z1000 from a Volkswagen, I can't tell you if that's a possibility.