There is a possibility that his love interest could be a mermaid. In the world of pirates, mermaids are often a part of the lore. A mermaid who saves Zoro from drowning or some other danger, and then they fall in love, would make for an exciting love story.
In addition to Tashigi, in the vast world of fan theories, there could be other potential characters who might be Zoro's love interest. But these are mostly just unfounded speculations. The main and most prominent one that stands out is Tashigi because of the way their stories intersect with each other in the context of swords and their personal growth related to swordsmanship.
The person Obito Uchiha was in love with was Rin. She was an important part of his life growing up in the Hidden Leaf Village. They had a connection that was rooted in their shared experiences as ninja trainees.
In the Bridgerton story, Eloise's love interest is Theo Sharpe. He is an interesting character who has different views from the upper - class society which draws Eloise to him.