Lenovo ZUK Z1, runs on Cyanogen OS can now be upgraded to Android 6.0 Marshmallow via unofficial CyanogenMod 13 custom ROM. Currently running on the Cyanogen OS 12.1, the ZUK Z1 is a great phone with first class hardware specs and mid-range price. However, ZUK Z1 users who are excited to tryout the new Android Marshmallow on their phone, read on to know how it is.
CyanogenMod 13 ROM for Lenovo ZUK Z1 mentioned below is an unofficial build and not yet stable for daily use. The CM 13 for ZUK Z1 is an experimental ROM and might have many bugs that have not been fixed yet. Most things are working fine, but GPS, Double Tap to Wake, Fingerprint Detection, Google Camera and SIM-Mode Switching crashes, which need to be fixed.
To install CM13 Android 6.0, your Lenovo ZUK Z1 should be unlocked, have root access and latest version of TWRP custom recovery installed on it. Do not forget to back up every data on your phone before installing the ROM.
Before you get start we remind you that the below method is for Lenovo ZUK Z1 with Cyanogen OS. Do not try it on ZUK Z1 with ZUK UI.
Warning: This procedure will void your device’s warranty. Follow the instruction at your own risk. We will not be liable if any damage occurs to your device and/or its components. It is recommended for technically talented users only.
2. Transfer both zip files to your phone’s SD card.
3. Reboot your phone into TWRP recovery mode. To do so, switch off the phone, press and hold the Volume Down, Volume Up and Power buttons few seconds.
4. In TWRP recovery, select ‘Wipe’ and clear cache, data and factory reset.
6. Return to main recovery menu, select ‘Wipe’ and clear cache and data.
7. Finally, reboot your ZUK Z1. It will take 10 – 30 seconds for the first boot. Once booted up, set up and Enjoy Android 6.0 Marshmallow.(Source)