This chapter has Oda highlighting something subtle here
Zoro gets taken down by a very weak Omen attack, less fanfare than what Hajdrujin took.
Sanji gets taken out by an actual Omen fire kick that causes the biggest explosion we’ve seen.
Thanks to his exoskeletons durability and regen, Oda is saying Sanji can take stronger attacks than Zoro. Since both are obviously coming back, Oda is only writing them temporarily out of the story