Also have it and did the same upgrade. It seems the only (or one of the few) upgradable Zenbooks. Others have SSD or RAM soldered on the board. Needed some spec

Also have it and did the same upgrade. It seems the only (or one of the few) upgradable Zenbooks. Others have SSD or RAM soldered on the board. Needed some special screw drivers though (torque 5) in order to open it. Ubuntu is running on it, has some quirks currently, but runs quite well, although I had to remove the splash from the UEFI boot options to have it boot from a USB stick. Without any special power saving options used (like having the dedicated graphics chip turned off) I get between 3 and 4 hours of battery. Once I have time I will try to tweak the Linux a bit to consume less energy, turn a few things off (keyboard backlight, bluetooth, lower screen brightness) , I should be able to get up to 7 hours of battery or so. On text-mode only I might even get more. The screen is really bright and has nice colors. Only thing I didn't like was the trackpad, so I'm mostly on keyboard.