Zosan in Modern AU where the StrawHats live in the same house
Robin and Franky share a bedroom. Robin spends time in the library with Chopper (who's just a normal 17y/o teenager) and Franky in the workshop with Usopp. Luffy and Zoro shares a bedroom and Sanji and Usopp shares one. Brooke and Jimbei shares one as well and Nami has one all to herself (but Vivi will sleep here when she visits).
When Ace came to visit Luffy, that's when Ace fell in love with Sanji. They got into a relationship for months. But then Ace goes away and they broke up because they agree they cannot handle long distance relationship.
Then Ace met Yamato and got in a relationship with him. When Sanji found out, he was miserable even though he admits that they are separated and should not feel this way. A part of him feels worse because Yamato looks feminine and attractive (him not knowing Yamato is a trans man) and thought that Ace likes women.
It turns out that Zoro had always have feelings for Sanji but he doesn't know how to express it. Zoro loves teasing Sanji because irritated Sanji is cute but now he wonders if Sanji just genuinely dislikes him. Before Zoro could do anything about it, Sanji was kidnapped.
Sanji was kidnapped by his father, who is the king of another kingdom and wanted Sanji to marry for political reasons. This time, the news is huge enough that Zeff and Sora also goes to try and save Sanji. Luffy, Nami, Brooke, Chopper and Zoro book a flight and got to the place as well. Similar things to WCI happened but Zoro felt like his heart break even more because he saw how Luffy treated Sanji and thinks that Luffy also loves Sanji. While he hasn't make any move.
The wedding crash was worse because now they also had the argument over the custody of Sanji and his siblings. Judge won the custody previously because he is a king and no one could go against him. But now, all of them are full grown adults and Sora and Zeff offered them a life as a normal human being, not a royalty who has to fight and they all agreed to go with Sora and Zeff.
On the flight home, Sanji's seat is next to Zoro so he finally got the time to get to know Sanji even more. As they talk, Sanji said that he needed a break from being in a relationship for a while and wanted to focus on himself. Zoro respects that decision.
When they reached home and everyone celebrated Sanji's return, Nami came over to Zoro and said "You liked him, don't you?" shocked, Zoro asked "What are you talking about?" "You like Sanji, don't you?" "Huh?? WHy would you think that?" "Bro, you're so obvious that only a dumbass would not notice. And unfortunately for you, Sanji IS a dumbass" "Then, what should I do? He said he wants to take a break. I don't want to force him." "It's okay. Just give him space. When he calmed down, then you can talk to him about it."
After a few years of dating, Zoro wanted to propose to Sanji so he met with Sora and Zeff. Zeff was already hard on Zoro and his "intentions" but Sora took it to the next level!!! In the end, Zeff had to calm Sora down and they both give their blessings.
Even on their wedding, there are still other men that disagree because they love Sanji so much but Zoro was going to fight all of them for it!!!
They had children and lived happily ever after!