Hi I am a Zed main from the SEA Server (SouthEast Asia). I started playing League at the end of Season 5 basically this is just my 2nd year becoming 3rd in League. I started playing Zed as he is one the most played Champion here is SEA after Yasuo, Vayne etc.
My First Provisional Ranked games were 10 straight Zed games making me 2-8 without even knowing the Basics of the champion. i ended up in Bronze 3 and later on fell on Bronze 5. The Next season I Learned the basics,the builds,counter and much more climbing my way out of Bronze 5 to Gold 5 in a limited time

Zed is an Assassin which is mostly played in the Mid Lane.
Zed is often picked as a champion to bully lane as he does a ton of damage if you hit his skill right. Zed can peel Marksman and Mages in a short period of time.

Here are the Pros and Cons of Zed:

PROS:
Can easily one shot opponent
An ADC have a really big problems with Zed as He can use a simple W E Q and kill the ADC quickly before they can even respond
Damage is high
Zed has the potential to one shot the backline of the enemy team leaving the frontline without and damage
Has an AoE
Zed can land skills W and E and cause damage to a group of enemies
Has an escape
Zed can easily go all in on 5 take out the ADC and go back from where he all in.This is all by the use of his Ultimate which is Deathmark and another of his skill W (Living shadow)

Cons:
Can Easily be countered
Zed has a really major problem with a high cc champions, If he ever take a CC it is most likely a Dead Zed on the map
Hard to Master
Zed is one the champions who cannot be mastered but a player can be a good zed player. You have to adapt to the situation and not rely on OneShotting Enemy or using simple Combos as this is really predictable coming from a Zed
When Left behind its hard to come back
Zed relies on Early game to much that losing the Early game can cost him the Game,Zed relies on quick all in on enemy and securing kills losing to much gold will delay his Items that are really important to have

Now let us talk about the spells that fit well with Zed :

Flash is a must on Zed it allow him to Dodge,Chase and Helps on Combos. Living Shadow cannot be the main source of escape for Zed as it is one of the core of his Combo.

Ignite would help Zed secure kills and reduce the healing of the enemies, Ignite gives Zeda quicker time to finish the kill than giving a 1-2 hp an Auto

Contempt for the Weak
INNATE: Zed's basic attacks against targets below 50% maximum health deal 6 / 8 / 10% of target's maximum health bonus magic damage.

Contempt for the Weak can only affect the same target once every few seconds.

Razor Shuriken
ACTIVE: Zed throws his spinning blades forward, dealing physical damage to all enemies they pass through, reduced to 60% against units beyond the first. Active Living Shadow , Living Shadows also throw a shuriken towards the target point.Additional shurikens hitting the same enemy only deal 75% damage.
PHYSICAL DAMAGE:»
80 / 115 / 150 / 185 / 220 (+ 90% bonus AD)
ADDITIONAL DAMAGE:»
60 / 86.25 / 112.5 / 138.75 / 165 (+ 67.5% bonus AD)

Living Shadow
FIRST CAST:
Zed's shadow dashes forward, remaining in place for 5 seconds and being able to mimic Razor Shuriken and Shadow Slash. Zed restores energy whenever Living Shadow lands a mimicked ability on the same target he does

SECOND CAST: While within 1300 units of each other, Zed and his shadow blink to their respective locations, swapping places.
ENERGY RESTORED:
30 / 35 / 40 / 45 / 50

Shadow Slash
ACTIVE: Zed and his Living Shadow Living Shadows slash, dealing physical damage to surrounding enemies.Enemies hit by a Living Shadow Living Shadow's Shadow Slash are Slow icon slowed for 1.5 seconds. Enemies hit by multiple slashes take no additional damage but are slowed by a 50% stronger slow.Each enemy champion hit by Zed's slash reduces Living Shadow Living Shadow's cooldown by 2 seconds.
PHYSICAL DAMAGE:
70 / 95 / 120 / 145 / 170 (+ 80% bonus AD)
SLOW:
20 / 25 / 30 / 35 / 40%

Death Mark PASSIVE
PASSIVE - REAPER OF SHADOWS: Scoring a takedown with/while Death Mark is active permanently grants Zed non-stacking bonus attack damage (he always keeps the highest value between his current bonus and his latest takedown).
BONUS AD:
5 (+ 5 / 10 / 15% of target's AD)

Death Mark
FIRST CAST: Zed becomes Playful untargetable for 0.75 seconds while dashing behind the target enemy champion, marking them on arrival, becoming Ghost ghosted for 3 seconds, and spawning a Living Shadow Living Shadow at the cast location which lasts for 6 seconds. Death Mark can be reactivated after 0.5 seconds of Zed's reappearance.

For the next 3 seconds, the mark stores a percentage of all physical and magic damage Zed deals to the target, detonating at the end of the duration to deal physical damage.


SECOND CAST: Regardless of distance between each other, Zed and Death Mark's Living Shadow Living Shadow blink to their respective locations, swapping places.
PHYSICAL DAMAGE:
100% AD (+ 25 / 35 / 45% of damage dealt)

LEVEL 1: start your Razor Shuriken,against a melee champions use your autoattacks as your way of getting minion and Razor Shuriken as a poke but against a Ranged champions it is better to stay back and use Razor Shuriken as your way of getting farm and poke aswell to utilize this it is better to hit both Champion and minion with Razor Shuriken

LEVEL 2: Personally I take Shadow Slash as my 2nd ability this allow Zed to farm under tower against aggressive enemies that can harass, however if you took control of the lane at Level 1 it is more efficient to take Living Shadow to harass enemies with a W Q

LEVEL 3-5: Harassing is the key, there are alot of players that cannot handle too much pressure constantly pressuring enemies can cause them to make mistakes that you should punish

LEVEL 6: You have the choice to roam or all in, Level 6 is Zed's spike where you can easily all in.

Before the 12 minute mark or earlier you should already have Duskblade of Draktharr or be late a little if you took Hexdrinker to have more survivability in lane

GUIDE WILL PROBABLY BE FINISHED BEFORE DECEMBER