Z wanted to bang her head on the wall. And look, there was one located nearby. Hufflepuffs, she thought ungraciously. And this one in particular!
"All right. Cards on the table. You know I can break through most spells you might put on the brooms and Professor Saporta likes me, so bringing me to the Slytherin Head of House and trying to lock me out won't be particularly effective. So, the best option would be for me to get my own broom, which means it'd be fantastic if you sent a letter to my parents saying I'm trustworthy and responsible and such. In return I could owe you a really big favor you get to call in anytime that isn't exams. Or I could get Slytherin House to generally respect you and the Quidditch equipment and games so you don't have to fight with them."