Some carrier firmwares come as .pkg . Use the official :

Users often look for specific "modded" versions to unlock the device for all SIM cards or to change IMEI/TTL settings for certain data plans. MF79U Quick Start Guide - FCC Report zte mf79u firmware

Zte Mf79u Firmware File

Some carrier firmwares come as .pkg . Use the official :

Users often look for specific "modded" versions to unlock the device for all SIM cards or to change IMEI/TTL settings for certain data plans. MF79U Quick Start Guide - FCC Report