thanks in advance! If you flash the Google Factory image you will lose root and the custom recovery but the bootloader will stay unlocked.

Can I flash stock ROM without unlocking bootloader?

Nope, only official roms can be flashed without unlocking bootloader.

Can I relock bootloader after stock ROM?

Download the Stock ROM and Recovery on the local storage of your device. Reboot your device into the custom recovery installed on your device and flash the Stock ROM and recovery. Once both utilities are flashed, your device should reboot with the Stock recovery and ROM installed. ...