Zoro claps. Sanji might be faster running but in combat the Shishi Sonson speedblitzes him lol. And no, they are not rivals. If you want to realize how rivalry works look at Kidd and Luffy. Both captains of important crews aiming to become the PK and both fellow Supernovas. A better rival for Zoro would be Killer. Both swordsman, fellow Supernovas and the right hand of a captain aiming to be the PK. Like fr; Google: "Rivals definition" and there you have. "A person or thing competing with another for the same objective or for superiority in the same field of activity." Not that hard.