Play aggressive before level 6. Dodge his Q and try to kill him in lvl 3 or 4 to gain an advantage, take advantage of the advantage you have gained. Do not push if you haven't vision of the map.

WHEN ZED USES HIS ULTIMATE
If he engage you with his ultimate just Shumpo (e) away of there and you'll dogde his Ult + Q combo.

WHEN YOU START HIM
[HAVING ZED HIS R] E + W is the combo. DON'T USE YOUR ULTIMATE AND Q, when he Ult to you, dodge his combos with shumpo and then you'll use your Q and ultimate to kill him (Q will reset your E) if he scapes you should have E again. [Normally he must be dead already] If he's not use your Ignite

[HAVING NOT ZED'S ULTIMATE] If Zed haven't Ultimate the combo will be E+W+Q+R, wait to reset your E with the W's blade and Shumpo to Q's blade if he's nearby (If he's not nearby to the blade, just Shumpo him). If he scape with lower HP use your Ignite.

Ignite + Deathfire Touch is very OP.