If you take a look at the op.gg in order to find the best Zed in Korea, you will find a couple of Zed mains. But based on win rate and rank in season 10, ZED99 outshine everyone else, and he is clearly the best Zed in Korea or arguably best Zed in the world.
ZED99 at the time of writing has a tremendous 65% win rate in the Korean challenger ladder with 750 LP. And a fun fact he doesn’t play anything but Zed. His op.gg if anyone interested.
He has a 65% win rate from 302 games with Zed having a 3.71:1 KDA. He also gets an average of 8 kills per game and only dies 3.6 times each game.
What Summoner spells ZED99 takes:
ZED99 always takes Flash and Ignite as his Summoner spells which is always ideal for any assassins.
ZED99 starts with his Q then E and unlocks his W at level 3. His skill order is: Q>E>W.
For the primary rune, ZED99 takes Electrocute which is very common among other Zed mains and assassins as well. In the Domination tree, he takes Taste of Blood to get some heal back when he goes all in, Zombie Ward which is very crucial for high elo games and Ultimate Hunter for some decent cooldown on his ultimate.
For secondary rune, he loves to take Transcendence and Scorch for extra damage.
ZED99 also has an alternative Rune which he takes against melee champions like Galio, Yasuo. Where he takes Conqueror as primary and Domination secondary.
When it comes to the item build path, he has a lot of diversity in it. He loves to start with a Long Sword and Refillable Potion and upgrade that Long Sword with a Serrated Dirk. But when he is matched with Melee champions he always starts with a Doran’s Blade.
From looking up his build order from his op.gg, he likes to upgrade his Serrated Dirk to Umbral Glaive if he has the gold early or completes the Youmuu’s Ghostblade as the first major item.
For boots, he takes the Ionian Boots of Lucidity most of the games or Mercury’s Treads if enemy has lots of CC.
For the first three core items, he takes Youmuu’s Ghostblade > Umbral Glaive > Edge of Night or Mortal Reminder. And build Duskblade of Draktharr as the fourth item which is very common among other Zed mains to build as first or second.