So now that you won't be able to qss zed ult anymore....

As someone said in a lengthy post about this already: positioning, and reliance on teammates. It's frustrating, but that's kinda how assassins work.

CC and peel stops all assassins.

The same way they deal with Rengar, Kha'zix and Talon.

But now what are Zed mains going to say counters him lol?

How dare you be able to nullify a champion's ability with an item! It's far more fair to allow a champion to nullify almost all abilities (Yasuo, Fizz) by super smart outplays (pressing E) than an item you have to purposely buy to get out of some obnoxious situations with champions that have abusive kits. Oh wait... Riot keeps saying that just because one thing is broken doesn't make it ok for other things to be broken. Great. Except they only address the new broken thing saying they will fix the other(s) 'later'.

I honestly despair with each major update. What next, stop potions healing if you take damage? Make you unable to cast an ability if the poor Zed might not be able to dive you under tower after farming safely and poking you to death? There are clear examples of changes that are stupid for the game's health but they go ahead anyway (feral flare, devourer, rageblade...) and say they prefer to change things and fix gradually. Meanwhile you can either play the game in the broken state or wait and hope for a fast fix.