You can't flash any zips without custom recovery, so yes you need to flash twrp. Also to get back stock it should be as easy as flashing a kdz file
Sent from my LG-D802 using XDA Premium 4 mobile app
XDA Developers was founded by developers, for developers. It is now a valuable resource for people who want to make the most of their mobile devices, from customizing the look and feel to adding new functionality.
Are you a developer?
Copyright © xda-developers. Hosted by Leaseweb