One of the finest budget phones of this… erm, last year was the ZUK Z2. I thought it could be a bit more polished on the software side, but the parent company certainly doesn’t agree.
Lenovo’s phones in China run the Vibe UI, which apparently isn’t getting too much love. Which is perhaps why the company is looking to make a switch to ZUI. It is believed that the switch will be in China only, at least for the time being.
The Moto Z (and Moto Z Play) is playing guinea pig for the testing that’s currently going on. There’s no word on how successful it is, but given the aggressive nature of Lenovo, you can expect to see the phone run official ZUI in a matter of weeks.
Lenovo’s ZUI recently made a switch from v2.0 based on Android 6.0 to v2.5, which is based on Android 7.0. Moto phones are usually among the first to receive Android updates, so it makes sense to base ZUI on the newest Android versions.