Here some ideas for both Kata and Zed that may help. (not sure if i can submit now)
Kata needs to be a bit "spookier". More etheral, more ghostlike. Maybe have her face paler, just throw in some make up ? I made a quick drawing to try make her more creepy/halloween like. If i'm allowed to share it i'd be happy to send it !
As for Zed, the most ...annoying are really his weapons. I just noticed the blades on his back are the same as Kata so i guess there is a story; but by the end, Q spell looks so goofy with a knife. Keeping the shurikens was really the best choice. Same for the claws, no idea why he has claws and it really make it awkward and clunky with his model.
I know you guys said you can't change the weapons at this point, but i feel like people would really be more forgiving with these skins if he had keep his original weapons... Isn't it possible to copy and paste weapons from another skin ? :o
Then, some minor esthetic choices i noticed on Zed.
Overall he could use a more ...Impressive appearence. He doesn't nearly look as threathening as a master of shadows using ghost could be.
Like, he need to feel overall like that spirit coming from the undead world reading to rip you out, right ? But rn with that armor he looks like he's too poor to afford a full outfit.
I think it could help a lot to just... Give him more armor. The midriff showing make absolutely no sense and looks super weird on Zed. It takes of his scary factor. So i'd say, if you guys could cover Zed a little more, especially that exposed stomach, i'd be more than thankful.
Another point i noted with him is how skinny he looks, compared to usual, but also his legs...don't fit with his upper body.
His legs are super frail and weak looking. I'd say, maybe bulk him up a little ? Or give him boots instead ? Just plain black knee boots could really work better than that...weird shoes + sorta black stocking ensemble.
Also perhaps make his mask more covering of his "face".
I don't think you could add him something majestic like a cape but one can dream :D
And finally (may works for Kata too) less blue. the blue here is too bright, so bright they look like Neon Unit and no spirits. Spirits are etheral, almost fading. I think it would gladly help to tone down the violent blue to something more soft, almost cloudy. Basically, more Kalista than Neon Strike Vi.
Just darkening the colors and toning down the brightness may be an exellent change to consider.
What i'm suggesting is super minor because i know you guys can't change really big points, but i think stuff like adding more armor can be discussed right ?
I may have spit on these skins quite a lot, but i frankly believe they can be saved (i may be biased because i'm a huge fan of Viktor and Zed and i like Kata too) so it be really sad to not change them and let them go live like this, especially since the community really has trouble accepting them to the point of wanting them scrapped :/
So i'll try to be more constructive and help a bit ! If my suggestions can make a difference.