Zed is a funny champion, you can confuse your enemies with your shadows (W), (R).
He's very safe, because you can escape of the enemy ganks just using your (W), you can walk across the walls.

Reds: x9 Damage

Yellows: x9 Armor

Blues: x9 M.Resist

Quint: x3 Damage.

21/9/0

Start with: Doran Shield + 1 poot of hp

First back: Bilgewater

Then u gotta for Brutalizer, and then finish your bilgewater to blade of the ruin king.

If you wanna roam you should buy boots, when you got lvl 11, when your power its really strong.

At this point u must choose, if your enemy is full ap, like veigar, leblanc, you should go for hexdrinker, if you are fine in lane, you should buy last whisper, and then finish your black cleaver.

Again you have to choose to go full damage buying the bloodthirster, or go more defensive and buy guardian angel.

In lane you have to arras with your combo W + double Q, everytime you can do that.

When you got your ulty, your combo is:
R + bilwater / blade of the ruin king + e + q, if he's escaping use your W to cath him, if he flash or somebody comes to kill you, you must use your W to run away.

In ranked play, if you wanna carry your team, you must win your lane and then help the other lanes. As soon as you got your ulty, you should go full in, probably your enemy will flash, at this point you have to arras your opponent, and wait for your ulty, when your ulty is up, probably you can kill your enemy midlaner.
When you have your lane controlled, you must help other lanes, with Zed you can engage with your W and then use your ulty, at this point you are in a 1v2 or 2v3 for that reason you will force flash's or they will die.

In teamfight's you should go for the enemy carry ad, if you cant go because he's playing very defensive, you should go for ap carry.

Pros: Easy farm with his passive.
Hard to gank.
Hard to counterpick.
Very strong at level 6.

Cons: He's a ninja.
No more cons.

Zed is a strong champion but his difficult is very high, you need to play a lot of games to control his style with shadows, when you do that you will beat everyone.

That's my first guide in english (not my mother tongue), I hope everyone can understand what I wanna say ;).