So, it's been a while since I've made an guide about assassins, so today I've made this for you guys as a thanks for your support for me.

Basically, you might wanna stick with lethality or damage runes for Zed. These runes might help with your damage burst, and it will also help for winning against the lane.

Thunderlord's Decree Is the best key stone for Zed since he's abilities is more damaging and bursting.

Yommous Ghostblade and Duskblade of Draktharr is one of the most important items for Zed. Yommous will help you at not only in chasing, but also with escaping. While Duskblade will help out clearing the wards that is placed somewhere that is close to you. These items will not only help you at chasing, damaging or even bursting, but it will help you to make more damage, as the armor penetration changes.

Ignite Is the major spell for Zed specially, he make damage by bursting.
Teleport Is an optional spell for Zed but, Ignite will do more.

When playing Ranked games, Zed has a possibility of getting banned so, you might be lucky in a game IF Zed will not be banned.

Pros
Cons
Merciless
dangerous
Merciless will help you to burst more not just damage!
Dangerous Game will help you to restore your health while in critical state!

Zed's passive is more like a critical to minions that is 40% below health so it will be easy to farm. Also try to get an advantage from your opponent to have a momentum.

Team work will do the trick, if you have a great team that won't flame, that won't be toxic, that won't be intentional feeding, you will have a great game and an easy one.

Zed's unique skill is all about Zed's ultimate, try to combo your opponent with Death Mark > Shadow Slash > Razor Shuriken > Living Shadow > Ignite then do a basic attack then press your ult again.