This official firmware (stock rom) for ZH&K Jumbo can help you un-brick or restore your device to its default or factory state.
If you have previously rooted or modified the system (or other) partition of the phone in any way, flashing this stock rom will overwrite all existing modified system files and replace with factory software.
If you have you have important data on the phone (like contacts, messages, app data, etc), please back them up because you could loose data after flashing.
Charge the phone to at least 30% so that the flashing process will not be interrupted by low battery. Interrupting the firmware installation means bricking your phone.
Download the firmware file from the link below and follow the recommended flashing instructions immediately after the download options. Please report any broken links discovered.
File Name: MT6580__JUMBO__JUMBO__ JUMBO__7.0__ALPS.L1.MP6.V2 _YUANDA6580.WE.L.rar
Size: 459 MB
Important! Always backup existing firmware before flashing any firmware.
After downloading the firmware from above link, extract the contents of the archive to an empty folder on your computer. Get a functional USB cable, then flash with Chinese Miracle II MTK (CM2 MTK).
If you have any questions or other contribution please post in comments section for assistance.
Credits: Lhezter, GSMDevelopers