Zed is a attack damage assassin that's purpose is to kill attack damage and ability power carries in teamfights so that your team can successfully win a fight.

After you have built your brutilizer immediately move on to building blade of the ruined king. This will help to increase your damage output with its attack speed and your survivability with its lifesteal. The unique passive it offers allows you to do even more burst damage with your combo and its unique active allows you to do the same while also being used as a gap closer.

Once you have completed the blade of the ruined king you can finish your youmuu's ghostblade. The unique active youmuu's ghost blade has gives you another gap closer/escape and has a low cool down. Youmuu's also gives you attack damage, cool down reduction armor penetration, and critical strike chance.

Once you finish that, your last core item is last whisper which allows you to shred through the small amount of armor that attack damage and ability power carries have.

Maw of malmortious is an item that you would get if you are dying a lot to ability power before you are able to successfully complete your combo. Also the stats aren't bad, it provides you with 60 attack damage, 40 magic resist, and 2 unique passives. One allows you to deal more damage as you take damage and the second allows you to absorb 400 ability power damage if that damage would have put you below 30% health.

Mercurial scimitar is purchased when the enemy team has a lot of crowd control abilities and is preventing you from doing pretty much anything. The unique active allows you to remove these debuffs and get in the fight. It also comes with some nice attack damage and magic resist.

Bloodthirster is purchased when you need more survivability. The unique passive shield can help soak up some damage while doing your combo and when hitting the enemy will give you life steal. It also comes with 80 attack damage.

Guardian angel is more often then not going to be your last buy. It gives you some good resist to both attack damage and ability power while also having a unique passive that revives you after dying which allows you to clean up any leftover targets.

Randuins omen is purchased when the enemy team has a lot of attack speed. This item gives you 100 armor and a unique active that slows down the enemies attack speed.

When choosing what to build for your last two items I would recommend Guardian Angel and Bloodthirster most of the time.

In the early laning phase of the game your combo will be WEQ. This will allow you to do easy poke damage by first putting your living shadow on top of the enemy and then using your E to slow them, which makes for an easy Q.

In teamfights your combo will be RWEQ. By initiating with your R this allows you to make use of the bonus damage your R can generate and it can be reactivated after completing the combo to pull you away from the enemy team.

Zed is a great mid laner who is great for bursting down carries. He has a high skill cap and his build can be diverse from mid to top to jungle. I hope you have a great time playing zed and that this build helped. If there is any think you think I might need to change, feel free to leave a comment. Thanks!