Zed's real problem is his w and q. the Q cost way too much for it to be, as riot puts it, 'your bread and butter'. His W has way too high of a cool down and the range + speed of the shadow itself isn't viable enough to make more than one use of it.

You can out run your shadow, so using it to go faster is stupid even with the double w tap. Your energy cost combos are too high to where you can't poke first before going into your ult, at least not in team fights.

HIs utls got a long cooldown too, but I can live with it.

Any AP carry or AD carry. Therefore he is working as intended. You're just bad.

preaty much anything that is not a tanky dps type

assassins don't usually 1v1 people. they tend to rip out about 60% of a target's health, then their steroids/cds stop them. meaning they want to get in on someone already hurt, or do enough to doom a full health target.

zed mostly has energy problems.

Zed is completely outclassed by other AD casters. His single slow has a pathetically small duration. The cooldown on his shadow is long enough that you can only use it once per engagement unless you have a minion wave to spam slash against, and that just makes you run out of energy so you still can't cast it.

He really needs his ult to kill people. The problem there is that the ult has pathetic damage by itself, and since Zed has no hard CC the would-be victim can just flash away from the ensuing damage.

And then there's the problem of his percentage AD bonus. It does nothing if you try to build the survivability that Zed needs. You could just stack AD, but that makes it very difficult to survive once you've used your ult already, since the shadow jump is pretty small.

Zed is worse than any other AD caster I can think of.

Any ad or ap carry I target. Then proceed to kill rest of enemy team with my awesome team.

Zed can assassinate just about anyone. I often see people playing him wrong though, either by getting poor items or poor builds. Getting things like crit or attack speed wont really help him, and playing top is just a bad decision all around.

Jungle for Zed is viable, but he mainly shines at mid as a roaming assassin. He can push his lane back to the turret quickly which gives yourself time to look for someone pushed out too far and take them out. Zed scales best with just straight AD and CDR, therefore your best bets are Ionian Boots, BT, Hydra, and LW as his core items.

Also, the ability order I find works the best are: getting Q to rank 3 by level 5, with a point each for W and E, then maxing straight E after your first point in R. At this point you should be around level 12, and can probably go back to finishing Q then W.