ZoSan

ZoSan is the slash ship between Zoro and Sanji from the One Piece fandom.

Canon
Zoro and Sanji didn't really like each other at the beginning. They fought and quarreled a lot, were annoyed by just each others personalities. But with time they grew closer and although they still don't agree in many things, they care about each other, even if they wouldn't say that out loud.

Baratie Arc
This is the arc, where Zoro and Sanji meet for the first time, though they don't share a longer conversation yet.

Sanji, back then, was an assistant chef in the Baratie, an ocean-going restaurant. Luffy, Zoro, Nami and Usopp needed to stay there for a while, because of an accidental, extensive damage Luffy caused to the resturant's ship.

After some time there, Zoro and Sanji share their first, short conversation. Zoro states that his goal is Grand Line too from now on, since he just learned that Hawk Eyes - the strongest swordsman in the world - is there too (and Zoro aspires to become the strongest swordsman in the world himself). Sanji comments it saying that Luffy and his crew are a bunch of morons, which probably are the ones dying first. Zoro says that he's right, but he didn't have to say the part about 'morons'. He says that from the time he decided to become the strongest swordsman in the world his life and death doesn't really matter to him and that he himself is the only person who can call him a moron. Then their conversation ends.

Soon afterwards the Baratie is attacked by Don Krieg's crew, which was also chased by Hawk Eyes - the same person Zoro wanted to find and take him on. After Zoro is beaten by Hawk Eyes and lands in the sea, Sanji recalls his and Zoro's previous conversation. Sanji calls Zoro a 'shitty idiot' in his thoughts, claiming that 'he totally lost his mind and he could just give up his dreams, he didn't have to die for them'.

Arlong Park Arc
During the battle with Arlong's men, Zoro fights with an octopus fish-man called Hatchan. Seemingly defeated with one strike, Sanji looks over to Zoro. He is punched by a ray fish-man named Kuroobi as he was distracted by Zoro.

Some time later in the battle, after Zoro has defeated Hatchan, Kuroobi attempts to finish off Zoro. Sanji, who was also seemingly defeated, comes to Zoro's rescue and kicks Kuroobi away.

After both Hatchan and Kuroobi seem to be defeated, Arlong himself enters the scene. Zoro tells Sanji that he can give him 30 seconds to grab Luffy. Hatchan, who was apparently not defeated, dives after Sanji. Zoro doesn't seemed to be worried, as Hatchan is covered in wounds and moving will reopen them. Sure enough, Hatchan's wounds reopen and Sanji makes a successful rescue.

In the aftermath, Sanji and Zoro can be seen sitting across from each other in an alley as Cocoyashi village celebrates the downfall of Arlong. They make small talk about each others wounds.

Filler Episodes
In the filler arc, the Apis arc, Sanji and Zoro are seen washing the dishes together. Here, Sanji uses Zoro's name, and neither of them bicker.

Reverse Mountain Arc
When the crew meets Crocus, Sanji attempts to communicate with him. Crocus ignores Sanji, causing him to get frustrated. Zoro calms him down and talks to Crocus instead.

Little Garden Arc
Upon arriving to “Little Garden”, Zoro announces he will take a walk after Luffy, Vivi and Karoo decide to explore the island. Sanji asks Zoro if he can bring back any edible meat, to which he responds with a smart remark challenging Sanji to see if he can get anything either. This annoys Sanji, and he enters the island exclaiming he’ll find kilos. Zoro declares they’ll compete in tons.

Eventually they re-meet with their catches. This ends in bickering and going back into the forest.

Filler Episodes
After the crew have left Alabasta and VIvi, they began sailing around the Grand Line again. While sailing, Nami spots an island. She yells for everyone to wake up. Sanji, hearing her voice, tries to ask for a morning kiss, but ends up nearly kissing Zoro as they are both half asleep. Before they wake up, it is shown that they had fallen asleep on a rug next to each other.

Skypiea Arc
In Upper Yard near the Sacrificial Altar, the Straw Hats decide to make camp. While cooking, Sanji forces Zoro to use his swords to carry a boulder to make stew. During dinner, Sanji is seen tossing Zoro a bowl of food, then sitting next to him.

Later, when the crew decides to split up in Upper Yard, Zoro gets lost. He decides to eat lunch, and speeds up his eating as a southbird has eyed the meal, which was made by Sanji. The southbird continues attempting to eat it and Zoro decides to fight it.

During Enel's plan to return Upper Yard to the Blue Sea, Zoro is seen sitting next to and watching over Sanji, who had been electrocuted by Enel.

After Zoro tells Chopper to treat WIper's wounds instead of his own, Sanji asks him why they should do that since they don't owe him anything. Zoro responds saying he doesn't understand his choice either but Wiper was fighting to the death. Sanji asks if it's sympathy, to which Zoro doesn't have an answer. A little afterwards, Zoro, Usopp, and Sanji are seen talking about the City of Gold together.

Filler Episodes
In the filler arc, the G-8 arc, the marines launch tear gas at Sanji, Zoro, Luffy and Usopp. Sanji is hindered immensely however Zoro is unaffected. Zoro makes a witty comment about this. After Luffy uses his whip attack, snagging Sanji and Zoro in it, Sanji yells at Luffy asking what he's doing. Then he turns to Zoro, calling him a "natural treasure" (referring to Zoro's "marimo" nickname) and asking him angrily about what he said before. They fight, as usual.

Long Ring Long Land Arc
Zoro and Sanji, surprisingly, hold conversations without arguing before the crew lands at a long vast plain for an island.

While discussing the Davy Back Fight, Zoro and Sanji both agree that the one thing they'd rather have than their life would be their pride.

Fanon
ZoSan is the one of the most popular ships in the One Piece fandom and at the same time the most popular slash ship in the fandom. It's a rival ship to SaNa. A big part of the One Piece fandom that enjoys Zoro x Sanji pairing usually ships ZoSan alongside with LuNa and Frobin.

Fandom
FAN FICTION

TUMBLR

PIXIV
 * Sanji/Zoro on Pixiv