for those who are like me and haven't felt the need to root their phone or use a custom recovery, the process below worked to update an unlocked, un-rooted, stock AT&T moto x. this is probably available elswhere on the forms too.
- copy the zip into "download" on the internal storage
- boot into bootloader by holding volume down and power together
- at the bootloader screen, use volume down and scroll to "recovery", then press volume up to select it
- in recovery mode you will see "no command". hold volume up and press power to show the recovery menu
- use volume down to go to "apply update from sdcard" then press power to enter
- you should be at "choose a package to install", use the volume buttons to highlight "download/" and press power
- use the volume buttons to highlight the zip and press power
the update will start. it took about 5 minutes on my device. when it finishes, use volume keys to select "restart system" and press power. device will restart and you're done.