Genetically, Columbus, Zeus and Tomahawk are identical. The flavor differences are terroir, or where they're grown. Even different batches of any one of them differ based on location. Columbus _may_ be more consistent since it's a proprietary version that's only grown on one farm.
Actually they different. Tomahawk and Columbus are the same, Zeus just got lumped in because of it's similarities. It is not the same. I think it has a bit more citrus, IMO