You can refer to format of bootanimation.zip from google source: bootanimation format
For VIMs Android, the boot animation is in /system/media/bootanimation.zip
It’s the same format used among all android bootanimation, you can try
to fetch the boot animation currently on the device:
adb pull /system/media/bootanimation.zip /some/destination/in/your/computer
to push the boot animation from your computer to override the one on the device
adb push /some/destination/in/your/computer/bootanimation.zip /system/media/bootanimation.zip
Cheers.