The reason why I think Zed is an...unhealthy champion
Hes got some good harass in lane and some good all in. That's cool.
The real problem, is the FAILSAFES.
No matter HOW badly zed fucks up, now matter how much he gets caught, he can just R or W for an instant escape unharmed.
If you don't have someone camping his shadow, (Which you shouldn't, thats 1 team member out of the fight) He will get out 100%. Unless you are a dumb zed and don't lead them between attacks and stand still, you can be in three places at once.
Where you are now, where you will be if you E, and where you will be when you R.
That is RIDICULOUS presence with an assassin. Leblanc had the same power, but in response they cut her silence so you can do something about it.
But zed still has EXTENDED untargetability. He got an extra .5 seconds of untargetability later after release, meaning he can dodge more damage, and follow you if you dash, flash, or whatever it may be. He can pursue, destroy, then blink away.
That's not good, Assassin's have an all in, and some form of safety, but the safety only lasts so long and there is a way to rid it.
For instance, Akali has her cloak, but it only lasts so long and can be negated by a pink ward.
Unless you CC Zed for a SIX SECONDS, which is TWICE as long as it takes for the mark to trigger, than he will get away.
The second thing, is that he can build nothing but tank shred, and still have more than enough damage to KO a squishy.
This is partially because tank shredding items are a bit too strong, but also because he has RIDICULOUS scaling and base damage.
BC, LW, and BOTRK for tank shredding, but i'm not a tank so that shouldn't do anything to me right? WRONG. He will scale off the slightest AD, and for some reason BOTRK actives APPLIES to his mark, dealing another half an active upon trigger, and his base damage is so sky high that without decent AD he still has massive damage to kill a 2k health carry.
This is why I think he is an unhealthy champion, no other champion in the game can build nothing but tank shred and KO a carry, then get out whenever he wants no matter how bad he fucks up.

), Zed R ignore everything.
3/ Fizz E is a dash and subjects to slow, Zed teleport is a blink.
4/ Fizz needs his E to kill, Zed always has his W for failsafe.
5/ Fizz needs mana/blue, Zed doesn't.
,
,
. He can get easily kited to death or CC'ed and if he uses his abilities as gap closers he has no escape and gets blown up.
Edit But I entirely agree on the tank shredding, APen items are really too strong and are the only reason I hate playing tanks because you're not tanky with those items floating around.
Give's both armor which already is awesome against Zed but the active just wrecks him entirely.