I main basically both champions and it pains me to say there is no clear way to counter a GOOD zed, yes i know it sounds horrible, and low ranked and all that but it's just true, a good zed will always beat a Yasuo, MY only advice is to play both champions, that way you know the cds and the capability of both champs, your best chance at winning is to beat him before level 6, and even then if he is a good zed he will still win after that IF you even got to beat him early on, because most Zeds know they cant win pre 6, so they passively farm till then.
As Dax said, use your E to go to minions to dodge his ult, Flash if you have to, whatever you do, avoid the AA, E, Q combo when he ults or you are guaranteed dead, while you dodge use your E,Q spin slice to get a tornado ready so you can just E and Q knock him up, ult to regain your flow, and go all out and hope for the best.
I play Both champions A LOT, i main Yasuo (here comes the flame) but Zed is my second most played, i know both of them inside and out, a good Zed will nearly always win, but as long as you can avoid his ult combo, you should be able to win, takes practice though.
E to minions when he ults you, Flash and E if you have to BUT WAIT TILL AFTER HE APPEARS, DO NOT, I REPEAT DO NOT FLASH OR E THE MOMENT HE ULTS YOU, it will waste your only chance of winning, you have to wait till he appears again, this is why i said to play both of them so you can learn when he appears so you know when to E to avoid his combo since you'll know right when he comes out again.
Here's another pointer, when zed ults It places him BEHIND YOU(most of the time, depends on positioning) , so obviously pick a minion to dash to sideways because he will expect to land an easy Q straight behind you, sooooo yeah there ya go, good luck rofl, it's a very tough match up, like i said i play both champions, i even have way less experience on Zed and i still destroy any Yasuo, but that's because i know both of them inside and out xD, good luck m8