I'm a Zed player so take that how you will.
Ungankable if he doesn't use his W to harass
Ok I'm going to take Kassadin, Leblanc, Azir, Corki, Modern Ahri, Morgana(With black shield) because those are the most recent competitive picks. All of these are "ungankable" if they don't use their gap closer(or black shield) to harass. Its the result of playing safely if the Zeds that you're ganking never use their W. Watch you're favorite streamer play Zed and they will use their W to harass extremely often and its on a punishable cooldown.
Clears entire waves with 2 spells.
The Zed is extremely farmed or fed if he can clear waves with 2 spells. QE, WQ, WE. None of those combos clear an entire wave alone. Just played a custom, it doesn't happen. PS: for fun I used just abilities to clear a wave w/o a canon and I needed 4 ability casts to do it.
Easiest last hitting in the game thanks to passive.
Yep, you're right. Although the one thing I'de say is the ones close to easy CSing is ADC because they build AD and AS and they are all ranged while Zed is a melee farmer if you're talking about CSing with his passive
"Get out of jail free" reactivation on his ultimate if things go south.
Is this not also a thing with LB? Malph? Sion?
Extremely good map pressure.
I'm not exactly sure what you mean by this. I would have assumed it meant split pushing and pressuring the other team to respond but then you mention his split pushing earlier in the post so I don't exactly have an answer for this one.
Forces you to build against him, while he still manages to get fed because Zhonya's doesn't exist at level 6
Again this is just part of the game for every champion, not just Zed. If I'm against an AP assassin I should go Athene's over Morello because it gives me MR. If I'm against malz, skarner, Zed, then I'de build QSS. If I'm a top laner going against an AP then I wouldn't go armor first. Zhonya's may not exist but you can for sure get seeker's by then, which gives a significant portion of armor in that stage of the game and is also along most AP mid's build paths anyway.
No real resource management
This one is extremely subjective. I couldn't endlessly spam Qs or WQs. The typical harass pattern is WEQ and AT MAX LEVEL it would cost you 125 energy to use that combo. If you landed both your and your shadow's Es then it would give you 40 energy back for a total of 85 energy cost IF you hit your E refund. on the other hand Zed's resource management isn't as bad as like Shen's.
Melts tanks just as easily as squishies thanks to LW, BC, Bork, Youmuu's.
Those 4 items cost 11200 gold assuming you bought 0 boots and just those items. Bjergson had an LB game on stream that he was 5/0/3 in with 250cs in 32:25 INCLUDING HIS BOOTS he had 9600 gold in items. Still coming short of the 11200 needed to buy just those 4 items you mentioned.
Zed certainly has his strengths; Hes good duelist, good splitpusher, pretty good item path, and has good escapability. But hes a melee, has extremely low kill pressure when he doesn't have ulti or its on CD, no CC, and is reliant on his skillshot Q hitting to get good kill pressure.
TL;DR: I disagree with OP with a side dish of some numbers