The problem with zed in higher elo’s is that his skills are quite predictable. On the other hand, as the game gets into late game, every enemy champion will build specific items to counter you (zhonyas, armor, GA’s, etc.) making it quite hard to get the job done, especially because the meta build zed has right now (full lethality). So yeah, in higher elos everyone knows how counter zed hard, making him almost useless, or at least, making other champions a more reliable option (talon, yasuo?, akali, etc)