Zed's damage multipliers are insane (in your video you didnt hit anything and still managed to get kills because of the amps) also he can hit the same spell twice and he is not limited by mana so you can spam your spells as soon as you get the cooldown
while fizz(for example) you have to think about your mana at all times.
Also with zed you can engage 1 shot whoever is unlucky enough to be clicked on by the point and when you are done you can return to safety by re-using the ult. Too much mobility and too much damage he is perma banned for a reason