You should absolutely be able to put the Cybex Cloud Z i-size on the Uppababy Vista stroller frame. The thing is, this, and even older Cybex car seats have the same attachment system, which is originally taken from Maxi-Cosi car seats. So all of the newer (I mean, no more than 7-10 years) Maxi-Cosi, Cybex, but also Joie, Kiddy, Recaro, Nuna, Avionaut, Clek Liing, and other car seats with the same attachment system CAN be clicked on the Vista frame WITH ADAPTERS.
These are the adaptors you need (for single mode):
They will accommodate all the car seats I mentioned.
You should either ask an Uppababy seller for their availability or get them pre-owned, meaning go through classifieds - as the Vista models changed from 2015 and used a different set of adapters (so don't bother getting the newer ones as they won't fit).