This is basically A Zed guide due to the patches nerfing Blade of the Ruined King's Active and buffing its Passive. By making him a duelist we benefit from our auto-attacks which the Passive from BOTRK boosts considerably and we relieve his dependence on his ult. Think of Master Yi almost when it comes to auto attacks.

Zed doesn't really synergize with his teammates very well but he's still useful. He helps by picking people off early game and can eliminate the stronger champion on the enemy team making team fights easier. Just wait for one of your teammates to initiate and if you can come in from behind, take out their player that is the most important (saving your Living Shadow to escape) you will certainly succeed.

Pros

He has insane burst potential.
His W provides quick exits.
He helps eliminate strong opposition in team fights.

Cons

Easily countered by Armor
Zed's Shadow Slash will only slow if your shadow hits them with it.
Very vulnerable after using your Living Shadow