"Are you crazy? The Dark Lord wants him alive!" Zabini said, and then gave him a clear wink.
"He'll be happier with him dead. Don't get in our way, Blaise!" Goyle growled.
"Harry?" Ron's voice called out confused.
Suddenly, spells were flying all over, but Zabini tackled Hermione, shielding her, as Goyle nearly killed her with Avada Kedavra. Ron managed to temporarily freeze Goyle, but Crabbe laughed and then shot out flames that expanded rapidly, incinerating everything. Harry grabbed Hermione and Ron and located some old broomsticks. They took flight as the room engulfed into menacing flames.
Harry turned toward the exit before he heard screaming. He couldn't leave... whoever behind. He swung his old broom back and spotted Zabini on top of the burning stacks and dueling Goyle. He nearly was blasted off the stacks by a nasty spell from Goyle, who was screaming for him to die. However, before Harry could reach them, the shelves that Goyle was on collapsed, and he fell screaming into the flames. Zabini nearly fell off, too.
Harry swooped down and Zabini clambered on behind him. "Thanks, Potter. Whoa! What the fuck! The exit's that way!"
"Forgot something!" Harry said, and swooped down to snatch up the diadem before the flames engulfed it.
He raced to the door where Ron and Hermione had made it through already. He almost crashed into the wall, but Zabini threw up a Cushioning Charm before they did. 
"Fuck, Potter! Learn to brake, idiot!"
"I was! The broom's Braking Charm is busted," he retorted as they got to their feet. 
However, the diadem screamed and melted as he held it up. Another Horcrux down.
"That must have been fiendfyre!" Hermione declared. "That was one of the ways to destroy a Horcrux. It was way too dangerous. I never would have tried that."
"Crabbe wasn't exactly a smart guy. Fucking asshole," Zabini murmured. "Wait, Horcrux? You made a horcrux, Potter?"
Ron, suddenly realizing that Zabini was there and upright, raised his wand at Zabini, who gave him a dark look. "Drop it!" Ron ordered.
"I just saved your girlfriend's life, Weasley," the dark-skinned Slytherin said, exasperated.
"You were in there with Crabbe and Goyle!"
"Who are dead, now. Good riddance. They were complete tools. I have no mark on my arm," Zabini said, and pulled up his sleeve. "Mother never did support the Dark Lord."
Harry didn't know what to say at first. "Lower it, Ron. He did save Hermione and he was actively helping us."
Ron reluctantly did.
"Thank you, O savior. We can call each other even for me saving your BFF's life. I owe you nothing."
"Fine. Now, what did you mean about Malfoy?" Harry pressed. He had to know... it was burning him. What Crabbe and Goyle had suggested... well... it wasn't pleasant. It had been nearly a month since Malfoy Manor.
"The fuck you care? You took his wand and left him there to die, Potter."
Harry spluttered, but there was shouting coming from the end of the hall. He could see Fred and George battling it out. Ron and Hermione went to back them up, and Harry slowly followed, Zabini at his side watching the duel.
"What happened to him?" Harry asked, again, realizing that he was feeling guilty for that unintended consequence.
"They... fuck we don't have time for this," Zabini started but suddenly shot a strong Protego that ricocheted a white spell. The spell went into the wall away from them, exploding it.