Here I am, playing Zac, one of two of my favorite junglers besides Sion, and suddenly out of the blue, people are just banning him like mad. What gives? They didn't change anything about him really besides QoL changes to his passive.
Did it really take you fools two years to figure he was this good or something or what?
Folks are playing carry toplaners, so people need a frontline Jungler. Metashifts in the jungle also favor him quite well
Reasons:
Give it a couple weeks and they will find another "OP" champion to obsess over.
His gank power with the E is just too strong. They buffed (doubled!) the knockup duration on it several patches ago and his ban rate has been rising steadily since. He's also the second-best jungler on champion.gg, which makes him the best at low elo since no one can play nidalee there.
I mean, he is incredibly hard to ward for. The range on his elastic sling shot is stupid long-- not to mention combined with his surprisingly high damage output. He's definitely been a strong champion (at least every time I have one in a game, I'm just crying) for a while, but I agree with the post below; nerfs to other champs made him shine brighter.
He got hit by "LCS Fever"
Wait till Preseason and he should go unnoticed again
zac has always been good
though i utterly suck at playing him :(
i guess the meta is starting to shift again
Thanks to range buffs on E he is very annoying to play against, especially if he camps you, since he can gank from so many different angles from such faraway distance it's ridiculous.
If he goes Runic Echoes he also does fuck ton of damage even if he goes tank after.
He been overshadowed 
