LOL, cause Big Mom and Kaido both attention is mainly on Luffy... they never even tried attacking Zoro at this point... they didn't attack Law or Kidd either... so their effort is only on Luffy, which is why Luffy gets some hand and help from Zoro.... if both Yonko focus On Zoro back to back attacks, Luffy too would step in and give a hand... but Luffy is the guy getting most of the pressure now, so he's 1st with all respect... but I give credit to Zoro that he's surely above the other three in showings...