The Hogwarts castle could be a refuge in the Z Nation fanfiction. Its protective spells could keep the zombies out.
In fanfiction, the post - apocalyptic landscapes of Z Nation could be magically altered by Harry Potter characters. For instance, they could use transfiguration spells to create barriers or shelters. And the magical creatures from Harry Potter, like hippogriffs, could be used for transportation in the dangerous Z Nation world.
A good 'Harry Potter Z Nation' fanfiction starts with a strong concept. You could have a crossover where the Death Eaters are using the zombie apocalypse as a distraction to take over Hogwarts. In terms of writing style, use vivid descriptions. Describe how the zombies look in the magical setting of Hogwarts. Is the Forbidden Forest full of lurking zombies? Also, don't forget about dialogue. Have the characters from both universes communicate in a way that makes sense. The survivors from Z Nation might use different slang than the wizards, and this can create interesting exchanges.
One interesting crossover could be the use of magic in the Z Nation apocalyptic world. For example, a wizard from Harry Potter might use spells to fight off zombies. Maybe a Patronus charm could be used to keep the zombies at bay as it's a powerful form of positive magic.
Well, in some fanfics, the honor code of the Yautja might blend with the Gryffindor's sense of bravery. A Yautja might respect a Gryffindor who shows great courage in the face of danger, just as they respect worthy opponents in their own culture.
The worlds might blend through the use of shared magical elements. For instance, both have magical creatures. The gargoyles' ability to turn to stone during the day and come alive at night could be related to some form of Transfiguration magic in the Harry Potter world.
One interesting 'Harry Potter Z Nation' fanfiction could be one where the characters from Harry Potter have to face the zombie apocalypse situation from Z Nation. For example, Harry and his friends might use magic to fight off the zombies. Maybe Hermione would try to find a magical cure for the zombie virus using her vast knowledge of spells and potions.
In these fanfictions, they blend by sharing certain characteristics. For example, the loyalty and camaraderie among the characters in both universes are emphasized. In Harry Potter, it's the loyalty among the students of Hogwarts and the Order of Phoenix. In Kancolle, it's the bond between the shipgirls. This common trait can be a basis for the two universes to interact, like the shipgirls and the wizards/witches working together based on mutual trust.
In fanfiction, the two universes blend in multiple ways. The characters from Harry Potter can be put into Creepypasta - like situations. For instance, Harry might find himself in a situation where he has to face a entity that is not from the wizarding world but from a Creepypasta realm and has to use his magic in a new and untested way to survive. Also, the magic in Harry Potter can be warped to fit the spooky nature of Creepypasta. Spells could have unexpected and disturbing side - effects that are more in line with Creepypasta. The creatures in Harry Potter can also be made more menacing by borrowing elements from Creepypasta. For example, a Hippogriff could be made to look more like a nightmarish beast with Creepypasta - inspired features.
The blend often occurs at a character level too. Characters from both series might form alliances or rivalries. A friendship between Legolas and Hermione could develop, with each sharing their knowledge of their respective worlds. Or perhaps Snape and Saruman could be pitted against each other, their cunning and knowledge of dark magic making for a great showdown. These character interactions help to bring the two very different worlds of 'Lotr' and 'Harry Potter' together in the fanfiction.
Well, in these fanfictions, the magical creatures in Harry Potter can be compared or even interact with Pokémon. The Hippogriff, for example, could be seen as a more magical version of a flying Pokémon. And the concept of magical potions could be used to create something that affects Pokémon in different ways, like a potion that makes a Pokémon stronger or more docile. The Portkey in Harry Potter could also be used to transport trainers and their Pokémon to different magical locations in the wizarding world.
The settings are very different. Fairy Tail has a more medieval - ish fantasy world with guilds spread across the land. There are various kingdoms and places full of magic and adventure. In contrast, Harry Potter is set mainly in a more modern - ish, hidden magical world in Britain. Hogwarts is a large castle school, and there are wizarding villages like Hogsmeade.