You Know What Would Make Zed Healthier?
A smaller Q range.
Full disclosure, I fucking hate Zed and I'm very biased, but hear me out. The number one complaint about Zed is that he's a low risk/high reward assassin. He has decent poke in lane and safe farm, which are two things that don't really make sense on a class that's supposed to be all about risk. On the farm side, reducing his Q range would make him suffer more for being pushed off of CS. On the assassination side, he wouldn't be able to so easily soften up his targets before going in.
With the above change it'd give room to lower his shadow cooldown, which is something I think is more much in line with Zed's fantasy than being safe and poking.