Rename the file to update.zip . Copy to root of SD card (not internal storage).

Download Fastboot ROM for Redmi 9A (e.g., dandelion_global_images_V12.5.8.0...tgz ). Extract it.

Boot phone into Fastboot mode (Volume Down + Power).

Select Install update.zip from SD card → Choose file → Confirm.

Download Mi Flash Tool (latest version).