Zoro and Robin are my 가장 좋아하는 couple in One Piece (even though it's not canon). Nami just seems to have a brother/sister relationship with Zoro nothing more.
Zoro in is the best couple. I ship Nami and Luffy so that means Nami is already taken. Besides Zoro and Robin both respects each other. I mean 당신 don't want to live with someone who annoys you.