update_app.py is a tiny tool for working with Huawei UPDATE.APP and
update.zip files.
The main (in fact, currently, only) function is to extract ROM images from the official stock ROMs.
If you've already got an update.zip file you extract all the contained images
by simply:
update_app.py update.zip
Depending on what the particular UPDATE.APP contains, you'll get files like
system, boot, recovery, and so on, extracted into the folder.
You'll also get several files that aren't really files as much as metadata.
The extracted images can then be flashed onto your device:
adb reboot bootloader
fastboot erase system
fastboot flash system system
Obviously, use this at your own risk. You might well brick your device in the process.