Coming from someone who plays a lot of Zed, I can imagine how it feels when your ultimate is countered by a simple item like QSS or a Zhonya's.
But here me out: The challenge of playing Zed is adapting to what the enemy is doing. If you see someone who rushed a Zhonya's, simply don't ult the person. Switch your target. Ult the adc. A thing about anyone other than AP Casters is that they'd have to rush a QSS for your ult. That's a very inefficient item, that gives MR. You'll still do damage.
Use your ult as a gap closer, use your W for damage, and then switch back to your ult shadow if you fail you kill him. Your abilities do amazing damage late game. Your autos hurt, extremely.
Look up a guide on Zed by Redmercy on Youtube, (a very good Zed main) he's mentioned some builds that go around Kayle ults, Zhonya's, invulnerability or QSS. usually involving strong autoattacks and burst instead of relying on the ult.
Also, the point of playing Zed is to use your skills to get early kills, so they struggle to get these counter-items. Once they manage to barely buy the Zhonya's, roam bottom and kill the ADC or Support.
The passive is very nice as it is right now. It's magic damage, which is hard enough to build against since they're forced to buy armor.
Please don't take this as me saying you don't know what you're doing or me saying you're wrong. This is me giving you an alternative instead of hoping Zed gets some sort of buff. He's actually very strong right now in terms of Assassins. Talon fell out, Akali's tankyshroud was nerfed a bit, Yasuo has been nerfed. Zed is in a great position right now. Try out what I suggested and see if it helps!
