In some fanfictions, their relationship might develop because of a common interest outside of spying. Say they both discover a love for a certain type of art or literature. This gives them a different side of their relationship to explore, away from the world of espionage.
Another way to develop their relationship is through misunderstandings. Maybe Cammie overhears something about Zach that she misinterprets. This causes a rift between them for a while, but as they work through it, they come to understand each other better and their relationship becomes stronger. Zach could also have his own insecurities about his place in Cammie's life, and as they talk about these things, their relationship progresses on a more emotional level.
Their relationship could develop uniquely if they had to go through a trust - building exercise that was really extreme. Like being locked in a room with a ticking time bomb and they have to disarm it together while sharing their deepest fears. This would bring them closer in a very intense way.
One idea could be that Zach and Cammie are on a secret mission together in a foreign country. They have to pretend to be a couple to blend in and gather intelligence. Along the way, they face many challenges that test their relationship and spy skills.
Another idea is that there's a new threat to the Gallagher Academy, and Cammie and Zach are the only ones who suspect it. They start their own investigation, which takes them on a wild adventure across different countries. Along the way, they encounter old enemies and make new allies, all while trying to figure out who is behind this new threat and how to stop it.
In fanfiction, their relationship would evolve a great deal. They would share a new bond because of the baby. There would be more tender moments between them. Zach might be more involved in Cammie's daily life, like making sure she eats well and gets enough rest. And Cammie would probably be more open with Zach about her feelings, especially those related to motherhood and the future of their family.
To develop their relationship in different ways, they could be put in a situation where they have to protect each other's secrets. This would create a strong bond of trust. For instance, if Merlin has a secret about his true origin that could put him in danger, and Nimue has to keep it safe. Or vice - versa. Their relationship could also grow through shared grief. If they both lose someone important to them due to the actions of an evil force, they can find solace in each other. Moreover, they could develop their relationship by exploring different magical realms together. As they encounter new and strange magics, they rely on each other more and more, and their relationship deepens.
Some Tumblr blogs are dedicated to specific fandoms and might have zach and cammie fanfiction. You can search for relevant tags like '#zach and cammie' or '#zach and cammie fanfiction' on Tumblr. But be aware that not all Tumblr posts are in the form of a traditional story.
Their relationship can be developed through shared secrets. For example, if they discover something about the academy that they're not supposed to know and have to keep it between them. This would create a deeper bond. Another way is through mutual protection. When one is in danger, the other steps up to defend, like Natsume using his fire Alice to protect Mikan from an attacking student. Also, they could develop their relationship by working on a project together for the academy. This would force them to spend time together, understand each other's strengths and weaknesses, and grow closer.
One great fanfiction is 'The Adventures of Cammie and Zach' which takes them on a thrilling spy mission outside of Gallagher Academy. It has really interesting character interactions.
Maybe in the fanfiction, Zach and Cammie are in a secret relationship. When Cammie discovers she's pregnant, they struggle with whether to keep it a secret or come out. There could be a lot of drama as they try to figure out how to balance their relationship, the pregnancy, and their own personal goals. For example, Cammie might be worried about how it will affect her future career plans, while Zach is trying to be the supportive partner she needs.
The main characters are Zach and Cammie. They are likely the focus of the fanfiction, especially with the big plot point of Cammie being pregnant.