@ycavan, a member of the XDA Developer forum, has successfully installed and booted Microsoft’s Windows 7 on the Asus ZenFone 2 without any major bug and runs smoothly.
The ZenFone 2 device is booted Windows 7 on it as well as Windows 8 (check videos below), and the thread also said Windows 10 could be installed and work well.
In order to install Windows 7 or Windows 8 into your ZenFone 2, you must unblock the bootloader, flash a specific KVM kernel, partition the SD card, and type a few of terminal commands.
This process is not for everyone and some skills needed to complete the task. But it’s still interesting to see this Intel-powered smartphone running a full version of Microsoft’s Windows. If you want to take the risk, follow instructions from here.