Very Unpopular Opinion
I do not think Zed necessarily needs nerfs. One of the main reasons as to why zed and other ad assassins like talon ( who is absolutely flying other the radar now), jayce and yasuo mid are so strong right now, is because tanks are in a very bad state. Historically, tanks always kept these mid laners in check because no one wants to run a full ad team, due to the fact that a team with 2 to 3 tanks hard poops on them, if they don't end early. Literally, on my smurf right now, which is g1, I've first, second, or third picked zed or jayce several times, and very seldom did the enemy team draft tanks. And if they did, it was usually just one.
I'm not saying zed isn't strong, he is, not op but strong, but he is more strong because of the meta rather than his kit. Most tanks arent meta, lulu, janna, and karma aren't meta, exh isn't meta. Zed is not the only ad mid seeing this amount of success and a quick search on other sites will reveal this.
I'm suggesting buffing armor items, removing the adaptive ratios on aftershock but increasing the hp scaling and/or introducing an armor/mr scaling, slightly nerfing penetration items, like lowering the total pen on each last whisper item (and last whisper itself), by 5 percent, and then slightly buffing enchanter items or enchanters themselves, nothing to drastic, just a little nudge. I think this will lead to a more balanced meta where assassins aren't as overbearing.
If you must nerf zed, I do not believe you should nerf both his q and w. You should nerf one or the other, preferably his q, as w is still his only means of trading with people. I'm saying this, because I know you guys have noticed that tanks are weak, enchanters are lackluster and doing work on bringing them back to speed, but I just don't want Zed to be sitting on a 46 percent win rate again when they are brought back to speed.