Zinnia doesn't die in the manga. The story progresses without that event. Usually, character deaths are significant plot points, but not in this case for Zinnia.
A 'pokemon zinnia fanfic' could be about many things. It might focus on Zinnia's adventures in the Pokemon world. Maybe it tells a story of her exploring new regions, encountering rare Pokemon, or her relationships with other characters in the Pokemon universe.
Popularity of 'pokemon zinnia slave fanfiction' is hard to gauge. Fanfiction popularity often depends on how well it's promoted within the fan community, the quality of writing, and the uniqueness of the concept. This particular fanfiction with the rather dark and potentially controversial'slave' idea may not be as well - known or widely read as other Pokemon fanfictions. It might only attract those who are interested in exploring more edgy or non - traditional interpretations of the Pokemon world, so it's likely not very popular in the general Pokemon fanfiction readership.
In short, NieR: Automata is a highly-acclaimed game that offers a unique gameplay experience and a thought-provoking narrative. It takes place in a world where machines and androids are at war, and players explore themes of identity, consciousness, and the meaning of existence.