This news is so sad. I understand why he needs time away though, fans and media alike were always super quick to accuse him of everything with the littlest proof. Hopefully he finds peace within himself and releases some awesome solo material!
As for the group now, Zayn's absence is going to be so noticeable. As well as feeling awful for Zayn, I feel particularly bad for Liam, since I think Zayn's departure is going to hit him the hardest. Just a really unfortunate situation for everyone.