To fuel such a fever long.

Zoro is a cambion, which means he feeds on sexual energy. A small crew like the Strawhats, its not normally enough to keep a cambion satisfied, but Sanji happens to be an abnormally sexually driven cook so it usually works out okay for Zoro. At least, it works out alright until Sanji finds out that Zoro's been taking energy from him through his dreams. For Sanji, he's trying to wade through the confusing mess of emotions for a certain marimo after a surprise kiss on the battle feild. It's not easy to do on a normal basis. It certainly isn't any easier when the man he has deeper feelings for is a cambion. Then everyone learns how important it is to keep their local cambion fed, for if they don't, someone might get eaten. literally.

Does what it says in the title, however the tone is less flippant than that.

Nami has an extremely uncomfortable reaction to an island's pollen, and Zoro offers to help.

Law suffers some well-deserved revenge from Ceasar following the events of Punk Hazard, and it's up to Kid to help him out. Set after the current events of the manga (~chapter 717 as of this posting).

The fight is brief and unsatisfying. The whole thing takes no more than five minutes and no more than two swords. They still hum for blood as Zoro sheathes them and faces the gang's growling, pissed off boss. “Fine,” the man shouts. “We’ll take you then, huh? Plenty of folks will pay to bring a big man down low,” he says nonsensically. “What—” A sharp pain in his ankle cuts him off. A downed man pulls a needle out of Zoro's skin.