Unable to Install TWRP / Cyanogenmod on Moto G 2013
As it's obviously the stock recovery you've used to flash CM, that won't work as it will do a signature check and thus reject the ZIP as being invalid. So here's what you do instead:


put cm-12.1-20151117-SNAPSHOT-YOG7DAO1K9-falcon.zip onto your device's SD card
boot into bootloader
now boot (not install) TWRP: fastboot boot twrp-3.0.2-0-falcon.img
TWRP will show up on your device. Chose "apply update from SD card", navigate to where you put your CM .zip, select it, confirm


Worked for me, though on a different device.