Should I learn Yasuo and zed

Well, it's a thing only you can decide. We don't know anything about you or your playstyle, and you provide no information on which we can base our opinions either, so yeah, they're both fun but mechanical intense, so if you want to put hours and hours into them, sure, go for it.

It took me ~6 months to be confident enough at Zed to hit plat with him, then he became meta and was 100% pick or ban and I had to learn completely new champs. I mean he was fun, but losing out to months of work isn't fun so I would suggest you take that into consideration before deciding.

Personally, I wouldn't bother with Yasuo and Zed since there are far more useful and reliable picks who are simpler to use competently.

If you are looking for reliable mid-laners in lower rankings, I would recommend trying:

If you learn them then you will have a greater understanding on how to counter them