I started playing Zed jungle recenty and I'm really enjoying it. So here's a guide.

Zed has a nice clear with his E and combined with his shadow can clear very fast.His shadow also provide him very good ganking potential and after level 6 you can 1 v 1anyone.Even it's not very much seen Zed is a viable option for jungling.

Always max E for the aoe damage, and in some cases maz Q if you're ganking a lot.Do not max W because it might give a nice boost of damage you need your other spells to assassinate the enemy carries.And always upgrade your ult.

Flash/Smite normal on junglers.If you play a lot of game in Zed jungle you can switch flash with ingite, but I wouldn't recommend.If your support has ignite you might want to take exhaust to chase down people, but you already have the Botrk active and Yommu's active, but the choice is up you.

You will sure get flamed and might have afkers if you pick Zed jungle in Ranked.But the chances are low because he is banned almost every game.If you happen to play Zed jungle you must practise a lot because Zed takes a lot of skill.

Pros

A great duelist

Great escape with W and R

High gank potential with W

Good late game

Can carry if played well


Cons

Squishy early

Might get shut down if he gets invaded

And vulnerable to CC

Always start Frog or Golems where your adc/supp is.Then get Blue and Red or vice versa (depends on side)After level 3 you can gank or keep farming until you get low and then back.
Zed clears fast and ganks easy.So abuse that because most people would underestimate a Zed jungle damage.And if you need to cover a lane don't worry your passive can make last hitting very easy.

Zed jungle is very rare seen but if you happen to play don't be surprised if you end up carrying the game.And practise a lot of normals if you ever decide to take this to ranked.All in all Zed is very viable and can turn around games even if he is behind, just by farming.So yeah don't hesitate and try it.