You gotta tell me what you want to do. How far are you gonna shoot? Are you shooting a match? Which one? What are the accuracy requirements?
The CZ is a great rifle. All I have seen and owned, like Lapua, SK, and Wolf best. All those ammos come from the same factory. It's all made by Lapua.
Federal GMM UM and GMM 922 are not made by Federal at all, they are made by RWS and are made on the R-50 line. I have seen some phenomenal lots of 922. It is best in hot humid weather, the best scores with 922 and UM will come in June July, and August.
RWS is worth a test for sure.
Eley is good to 100 yds. It is garbage after that.
Testing 22 ammo is where one truly learns that moa is not linear. What I mean is this; 1" groups at 100 does not equate to 2" at 200. You do not know what it will do at 200 yds unless you ACTUALLY group it at 200...Period...End of story. My best 200 yd ammo has never been a great 50 yd ammo. And I have tested a LOT of ammo in 22 rifles.
Test your ammo at its maximum range at which you plan to use it, up to about 240yds past 240 yds I have found they all get sketchy in ANY gun. I have shot quite a bit at 300 but it isn't very predictable.
22rimfire performs best in hoT humid conditions. If you test your ammo at 60 degrees, it won't perform the same at 90, I promise you. If you are shooting below 50 degrees you need to test some polar biathlon.
If I didn't mention it, it doesn't go in my match rifles.