Oops. On my HTC One (M7), it's actually trying to push JellyBean 4.3 on top of JellyBean 4.2.2 that was out-of-the-box.
EXECUTIVE SUMMARY: (1) Allow the .zip file containing the update to download into the phone’s protected cache partition. (2) Reboot the phone into its low-level “RecoveryMode”...