"Nicotine."

Zayn knows what he's doing.
I mean that's what he thinks.
All he's doing is breaking the ones around him that care the most about him.
He was innocent. He was the one with all the Mickey Mouse shirts, not the one with all the cigarettes or that one boy he saw exclusively and only him Luke Hemmings.
He left Liam because Liam killed Niall. I mean thats what he likes to think and honestly if you tell him otherwise, I advise you don't.
He's a sex machine, gay, drug abuser, and upright a jerk. But the most important thing is, he envies Liam.