Not much really happened in this chapter.
Still no idea what's up with Sanji. Oda seems to be quite fond of drawing plot revelations out lately, such as having the samurai agree to tell the Strawhats everything going with them once they reach the top of Zou and then having them repeatedly fall back down. I guess Oda wants to tell us everything in a certain order for maximum dramatic effect, but the ways he's doing so to make that happen just feels contrived. He didn't even give a reason for not telling us about Sanji - he just skipped that conversation and then had the characters talk ambiguously about it so the reader won't find out. The fact that Oda is acting like this, though, makes me partially predict that it's going to be something comedic. We see Brook again in this chapter, and Momosuke is mentioned, although no Ceasar Clown (and obviously no Sanji).
We got a flashback to how the crew evaded the Big Mom pirates, which I wasn't expecting but was glad to see. I think the relative ease at which half the strawhat crew were able to escape a Yonkou's flagship makes the Big Mom pirates look a little weak, although I suppose if she herself had made an appearance it may have turned out much differently.
It's hard to predict what the conflict of this arc will end up being at this point, but the two most likely contenders will either be the samurai or Zou's King of Night Nekomamushi. Possibly the King of Day Inuarashi and he will have some disagreement concerning the visitors to the island, and Nekomamushi might attempt to attack the strawhats. Or the samurai arrive and one or both of the kings will attempt to take their revenge on them, thus forcing the strawhats to intervene.
Is Jack a Mammoth Ancient Zoan? That would be pretty cool.