Zed is probably atm the best AD anti-carry in the game. His ability to take down a target in teamfight, thanks to his ultimate, makes him a pain to deal with for the enemy team. He's also the best farmer in the game, no mana reliant, he can afk farm very easily then crush the entire enemy team later in the game.
Very strong in soloQ and 5x5 premade thanks to his splitpushing ability.
This guide will deal with Zed top and mid on Summoner's Rift.

Enjoy!

When should I pick Zed ?

Strong pick in SoloQ and 5x5 premade.
There are many threats damage in your team (3 at least).
Your team got CC and a good engage.
The enemy team isn't tanky.
You can hard counter pick a champ (= snowball!).

The last rule isn't very important compared to the others.

When is Zed a bad pick ?

Special one for Zed :
Against Double or Triple AP Team Comp (more Zhonya).
You have to engage every teamfight.
Your team doesn't have any CC.
They got
The enemy team got many shields.

Base Stats :


Damage 49 (+3.4 / per level)
Attack speed 0.658 (+3.1% / per level)
Health 445 (+80 / per level)
Energy 200 (+0 / per level)
Move Speed 345
Armor 17 (+3.5 / per level)
Spell Block 30 (+1.25 / per level)
Health Regen 6 (+0.65 / per level)

Pros :

Huge single target damage.
Good AoE damages.
Easy farming.
Snowball very hard.
Many escapes.
Fun to play.
Energy instead of mana.
He's a ninj4!!

Cons :

Melee AD.
Totally countered by one item : Zhonya's Hourglass
Need a CC team to be truly effective.
Very item dependent.
Hard to carry 1v9 as Zed (no real reset, no snowball ability in teamfight)