According to the configuration manual (page 225), you will need to follow the below steps to update firmware for multiple devices at the same time:
Best practice would be to first update only one camera and in a second step, to update max. 10 cameras in parallel.
If you use the combined firmware file, you can upgrade any camera simultaneously, regardless of the CPP platform.
If you use the firmware files that are dedicated to a certain CPP platform, then you will need to select simultaneously only the cameras with the same CPP platform.
The firmware files can be downloaded from the Download Store, in the tab Firmware > Cameras and Encoders: https://downloadstore.boschsecurity.com/index.php