Hello Fellow Zed players!
This guide will bring you something to use to help you carry as an assassin. I am going to try and be as quick and straight forward as possible, as this is suppose to help you quickly climb the ladder of league.
A little about me:
I am Bronze II and am moving up quickly due to my many shortcuts I am finding! This is one of them, I have only used it twice, but did quite well each time.
I hope you all enjoy this guide and find it as useful as I did!

The MR really helps against most mid lane champions, but you may be asking, why CDR/level vs more MR or flat CDR. As most may know, and that I have found out, if farmed well and not completely failing, Zed is a late game champion and is a threat in every game unless shutdown. Therefore the per level CDR is more worth it late game, where Zed shines.
The flat armor helps him against most of his weaknesses, because a lot of them are melee.
The armor penetration is great because it allows for early game damage to be dealt easily as well as opening the chance to grab The Brutalizer after you get the Cutlass.
Attack Damage never hurt anyone, right? Wrong, it hurts your opponents. Badly.

The selected masteries help a lot with Zed and his abilities, as well as give him a little bit of a health buffer.

Once again, the Cutlass is a great option to grab first because of the life steal, but The Brutalizer is a usual start for Zed because of the Armor Pen. Just folow the order and I believe you will be just fine! Armor Pen + Attack Damage is obviously the most lethal combination.

Like I said, quick guide, but its like a short and sweet thing, eh?
Thank you again, and happy leaguing!