The human soldier would first have to adapt to the different physical environment. For example, getting used to living among ponies instead of humans. He might also need to learn the local language and customs.
He would need to find a new way to use his soldier skills. Since Equestria has its own set of rules and ways of dealing with problems, he can't just rely on brute force. Maybe he starts training the ponies in self - defense in a way that suits their abilities.
The human soldier could interact in a more professional way at first. If he's on a mission, he would treat the animals as allies or informants. He'd ask them for information about certain areas or events in Zootopia. As time goes on, he might start to develop personal relationships. He could share stories of his own world with them, like battles he's been in, which would fascinate the animals.
One possible storyline could be the human soldier teaching the ponies in Equestria new combat strategies. Since human warfare often involves complex tactics, it would be fascinating to see how the ponies adapt to them.
Well, perhaps the human soldier arrives in Equestria through some sort of magical portal. Once there, they might have to adapt to the different culture and magic. They could start by learning about the Elements of Harmony and use their soldier discipline to help in times of crisis. For example, when there's an invasion of some dark creatures, the human soldier's knowledge of warfare could be crucial in formulating a defense plan.
Some fanfictions might depict the MLP being excited. They could see the human as a novelty, something completely different from what they're used to in Equestria. They might immediately start asking questions, like where the human came from and what their world is like.
Naruto would adapt slowly. At first, he'd be confused by the different lifestyle. But his adaptable nature would help. He might start by learning about the local customs and trying to fit in at school. He'd use his ninja skills in secret, like using his speed to be on time for classes when he oversleeps.
In a fanfiction, RWBY's adaptation to Earth life would be a complex process. Ruby would be drawn to the bright and shiny aspects of Earth, like big cities and new gadgets. She might start a blog or a YouTube channel about her experiences. Weiss would struggle at first with the lack of the familiar caste system from Remnant. But she'd eventually find her place, perhaps in the art or fashion world on Earth. Blake would be on the lookout for any signs of discrimination similar to what the Faunus face on Remnant. She might get involved in activism if she found such issues. Yang would be all about experiencing new thrills. She could become a popular figure in extreme sports or in local bars where she'd show off her strength in friendly competitions. Their Semblances would also play a role. Ruby's speed could make her a star athlete, Weiss' glyphs could be used in magic shows (if Earth has something like that), Blake's shadow - like abilities could be used for cool stunts, and Yang's strength would always be an attention - getter.
The human soldier might act as a mediator between different factions in Equestria. Since they come from a different world, they could have a more objective view. They could also be a source of new ideas, like different ways of training or organizing for defense. And in some cases, they could be a bridge between the human world (if it exists in the fanfic's concept) and Equestria, facilitating trade or cultural exchange.
The human soldier might be in awe of Judy Hopps' determination. He would probably respect her for her tenacity in a world where she has to prove herself constantly. With Nick Wilde, he could initially be a bit suspicious as Nick has that sly fox charm. But they might bond over their shared experiences of being outsiders in some ways. He could also befriend Clawhauser, enjoying his friendly and laid - back nature, and sharing stories of his military life with him over donuts.
The human soldier could interact with the police characters like Judy Hopps and Nick Wilde. They might start off with some misunderstandings as the animals in Zootopia are not used to humans. But eventually, they could team up to solve crimes or deal with threats. For example, if there was a criminal using human - made weapons, the human soldier's knowledge would be useful.
He'd have to learn the new rules. Percy is used to the Greek pantheon's way of doing things, but in Asgard, it's a whole different ballgame. He'd probably start by observing how the Norse gods and their followers interact. And he might use his charm, which has served him well in the Greek world, to make friends among the Norse.