qss'ing Zed's ultimate Q & A
Removes all disables (excluding Suppression) and summoner spells debuffs affecting your champion and grants 65% crowd control reduction for 3 seconds.
Zed ult =/= disable
Removes all debuffs from your champion. 90 second cooldown.
Zed ult = debuff
If you havn't seen faker's 1v1 zed highlight, he uses skill but also he had QSS, thats how he won
http://www.youtube.com/watch?v=da09LgzA0sY - go look.
As for cleanse, im almost 99% sure it doesn't cleanse zed ult.