the fight so far has been Luffy trying to figure a weak point or a way to defeat Kaido, that's what was he trying to accomplish two chapters ago while the rest try to protect him
so Zolo wasn't even close to Luffy to begin with, he just helped giving him time to adjust to Kaido powers
what's more interesting is Kidd now is tasked to deal with another Yonko
based on this Zolo is far from being compared to Luffy and Kidd, it's just common sense to consider Zolo around Killer lvl and way behind the Captains trio