So why Life Steal zed? I remember that everyone was playing him like that in season 4. Im a huge Bjergsen Fan and he did build like this and he played with these runes ( ofc there was no Duskblade so u did something else (BlackClever or GA )

Life Steal Zed is still really great pick. You can stay alive in Teamfight after few AA to get your life back. Its important coz this game rely on teamfights ;)

Standard runes with some LifeSteal.
Its good
Its Retro

Gives u great start if u get poked a lot
With Dorans Blade u have 10% life steal at start

12/18 - nothing special, typical masteries for assasins

Damn these chapters are long :D

ok So lets go Pros / Cons

Pros:

- GREAT sustain
- Good 1v1 sytuation if u're fed
- Easy snowball and roam
- DMG from hell post 6lvl

Cons:

- Easy to counter, just zhonyas
- Late game is mmm meh if u dont focus correctly
- Easy counter by adc, QSS
- If u get behind you're pretty much screwed and u lost

This is the easiest part tho
Just use ur passive, its great for farming
And with the sustain mmmmmmmm perfect

Zed is one of the srongest assassins in the game right now in my opinion

He has great potential to carry
Life Steal on him is just great coz u can solo everybody (yes, even rammus)
If u get fed = GG
If u outfarm your enemy on mid without kills = GG
Of Course this is one of the hardest champs in League but after mastering him u can win every game

Master him, Master the Shadow