If anything at Hogwarts could be considered truly odd, it would be the friendship of Zara Lynch and Cedric Diggory. Diggory was a Hufflepuff and Lynch a Slytherin, and while the rivalry wasn't as strong with Hufflepuff as it was with Gryffindor or Ravenclaw, it was still there. But the two were nearly inseparable, despite nearly having no classes together. They ate meals together, – always at the Hufflepuff table – they were always studying together in the library, and whenever they had free time, they spent it out on the grounds by the lake or somewhere in the Hufflepuff dorms.
Zara and Cedric just clicked. They knew their friendship didn't make sense to anyone else, but it made sense to them, and that was all that mattered. Zara actually cared about Cedric more than his looks. Yes, he was handsome, but that wasn't what made him Cedric. What made him Cedric was the way he'd always swat at her and complain when she messed up his perfect hair, the fact that he loved Charms despite being horrible at it and how he was a prodigy at Ancient Runes, but despised the subject. He was Cedric because he, the epitome of all things Hufflepuff, would complain about homework and Snape just like every other student, because he had a crush on a Ravenclaw in their year and despaired that she would never really see him. Yes, he was kind and loyal, just and hardworking, but those things weren't what made him her best friend. He was her best friend simply because he was Cedric, and all those traits he had just helped him to see past the emblem on her robes and see her for who she was.
Likewise, Zara wasn't just a Slytherin. Sure, she was a Snake, but she was human too, and unlike the rest of her house, she actually let loose and showed her emotions freely. She didn't mind getting dirty and she loved Quidditch almost as much as Oliver Wood did. Not that anyone but Cedric knew that, because no one but Cedric cared. She didn't care what people thought if they caught her out by the lake wrestling with Cedric, or if anyone approved of her waking up all the boys in the fifth years' boys' dorm so that she could drag poor Cedric out of bed at two thirty in the morning because O. were two days away and she was panicking and needed him to help her study. She laughed and joked around, she was human. She loved Transfiguration because the concept of it baffled her and hated Potions because, in her words 'Snape is a dick.' She didn't care about image, or blood purity. She only cared if you pissed her off or not. She teased Cedric about his crush on Cho, laughed when they both realized that dozens of other boys in different Houses, including Harry Potter, had a crush on the girl too. He wasn't 'pretty boy Cedric Diggory' to Zara, he was 'dumbass, get out there and make a move.' She was warm and kind, sarcastic and witty. Yeah, she was cunning and ambitious, it was those very traits that put her in Slytherin, but she wasn't manipulative or cruel, she wasn't evil. She was good. She was brave, loyal, and intelligent too. She also wanted to be Head of the DMLE someday, and straighten out the Ministry. She wanted to make the government less corrupt. That didn't mean she didn't know how to use her cunning to her advantage. She definitely did, and she used it often. However, she didn't think herself above anyone else or think certain people didn't deserve magic. She just made sure certain events went the way she wanted, when she wanted.
Despite all their differences, they were also the same, and with as much time as they spent together, certain traits did rub off on the other. It was cunning and a healthy dose of paranoia he learned from Zara that helped Cedric survive that night in the graveyard. And it was humility she learned from Cedric that allowed Zara to visit Harry Potter in the infirmary afterwards, grasp his hand, kiss his brow, look into his haunted emerald eyes, and say 'thank you.'
Despite the oddness of their friendship, they were friends, and they wouldn't have it any other way.