Zoe could be a new student at Hogwarts who gets into trouble. Maybe she's a first - year who wandered into the Forbidden Forest by accident and Harry has to save her from the dangerous creatures there.
Well, perhaps Zoe is in danger from dark wizards. Harry, with his skills and bravery, could use spells like Expelliarmus to disarm the villains threatening Zoe. He might also use his invisibility cloak to sneak up on them.
If Percy saves Zoe, it would likely have a significant impact. Maybe it unlocks hidden powers for Percy or makes Zoe more dependent on him. There are so many possibilities for how this could unfold.
There is. A lot of fanfiction writers like to blend different fictional universes or introduce new characters into existing ones. In the case of 'Harry Potter Zoe Nightshade' fanfiction, it might involve Zoe Nightshade somehow getting involved in the magical world of Harry Potter. Maybe she's a new student, or she has some special connection to the wizarding world that gets uncovered in the story.
One common theme could be friendship. How Zoe Nightshade forms friendships with the characters from Harry Potter. Another could be adventure, as she joins them on their quests in the wizarding world.
One common theme is the clash of different magical worlds. Since Zoe Nightshade comes from a different mythological and magical background, seeing how her world's magic interacts with the magic in Harry Potter's world is often explored.
A common plot element is Percy using his powers. For example, his control over water might play a crucial role in saving Zoe. Maybe he creates a water shield to protect her from some sort of attack.
One popular 'percy saves zoe fanfiction' might be found on FanFiction.net. You can simply search for that exact phrase on the site. There are often many talented authors who create interesting stories around this concept.