It had a bug where the chroma skins were occasionally using Classic Zed's spell and idle animation particles instead of Shockblade Zed's particles.
Not sure if that should take 3 months to fix, I dunno. But hey it's a reason I guess.
But what we really should be hoping for, is new colors/massive upgrades to the current ones. Shockblade Zed is such an easy skin to chroma that there should really be no excuse for making them look bad. The absence of a black chroma, despite Zed having many defining features, is highly unfortunate. The yellow is waaay too flamboyant, the purple is too soft around the edges and feminine. Many others agreed with me in the skins forums about these aspects of the chroma, but all we can do is wait and see. I just hope that the bug isn't the only thing they're working on, especially when it's been taking THIS long.