This is the official page, from which you can download the Official ZTU K9 Stock Firmware ROM (flash file) on your Computer. The Firmware Package comes as a zip file which contains the Firmware, Flash Tool, Driver and How-to Flash Guide.
Download ZTU K9 Stock ROM (flash file)
How to Flash ZTU K9 Stock ROM
Step 1: Download and Extract the ZTU K9 Stock Firmware on your Computer.
Step 3: Now, Install the provided USB Driver on your Computer.
Step 4: Once Driver is installed, Open Flash Tool on your Computer.
Step 5: Once Flash Tool is Launched, Connect your Device to the Computer using the USB Cable.
Step 7: Once flashing is completed, Disconnect your ZTU K9 device from the Computer and Restart the Device.
[*] Flash Tool: If you are looking for the latest version of SPD Flash Tool, then head over to SPD Flash Tool for Windows page.