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.
One day, Zoro got lost as usual on the ship. Nami found him and instead of scolding, she showed him the way with a smile. Since then, Zoro started to notice Nami more. Their relationship grew slowly as they fought side by side against enemies. Zoro would always protect Nami in battles, and Nami would patch up Zoro's wounds after. It was a quiet, budding love story.