I'm not sure if there is an exact fanfiction titled 'naruto is this a zombie crossover fanfiction'. There are countless fanfictions out there, and it could exist, but without searching specific fanfiction platforms, it's hard to say for certain.
It could be. It depends on the specific plot and characters involved. If there are elements from different zombie-related universes combined, then yes.
The theme of human nature also often appears. In the extreme situation of a zombie crossover, some characters may show their best side, like selflessness and heroism in helping others survive. But others may show their worst, becoming selfish or even cruel. Writers use this to explore how people really are when pushed to the limit in these strange and dangerous crossovers.
The Volturi could be great antagonists. They might see the zombie outbreak as a threat to their vampire world order. They could try to wipe out all the zombies and anyone associated with them, including Bella if she has any connection to the zombies.
It could be about Naruto and his ninja friends suddenly finding themselves in a world overrun by zombies. They would then have to use their ninja skills to survive and fight off the zombie hordes.
One possible plot could be that a powerful necromancer from the Naruto world accidentally unleashes a zombie plague. Naruto and his friends have to not only fight their zombified comrades but also find a way to reverse the spell. They could use their ninja skills in unique ways, like using shadow clones to distract the zombies while they search for a cure.
Well, it could be about the survivors from Left 4 Dead finding themselves in a world overrun by Nazi zombies. They might have to use their skills and weapons from their own world to fight these new and more menacing foes. Maybe they team up with some resistance fighters who have been battling the Nazi zombies for a while.
One idea could be that Bella, instead of becoming a vampire, is bitten by a zombie. She then has to struggle with her new zombie nature while still holding onto her humanity. For example, she might try to resist the urge to attack her human friends like Jacob and Charlie.
There are also 'zombie crossover fanfiction' that combines zombies with a fantasy world like Middle - earth from 'The Lord of the Rings'. Picture hobbits and elves trying to survive a zombie outbreak. It adds a whole new layer of drama and adventure to the familiar fantasy setting. Usually, the writers play with the different abilities and cultures in Middle - earth to create unique survival strategies against the zombies.
Sasuke could be really engaging in this scenario. His cold and calculating nature would be a contrast to the chaos of the zombies. He might see the zombie outbreak as an opportunity to gain more power or find a way to use the situation to his advantage against his enemies in the Naruto world. And his Sharingan could potentially have some new abilities when dealing with the undead.