This is a full firmware restore (not just an OTA update). It will wipe your device and install a fresh version of OS 10.3.3.
Join a BlackBerry Legacy group (search Telegram for "BlackBerry 10 Lounge"). They maintain rolling mirrors. Look for a file with STL100-2 and 10.3.3 in the same name. Blackberry Z10 Stl100-2 Autoloader 10.3.3 Download