Thanks for coming back to me !
I wouldn't be able to give you an exact answer, so I suggest that you contact HP directly for a clear and precise answer.
Some computers require specific hardware and motherboards to accommodate a WWAN module, enabling a 4G/LTE or 5G connection.
If you don't have this hardware (factory-installed), it may not be possible to install afterward...
For reference, here's a link to the HP ZBook Firefly 15 G7 Maintenance and Service guide : https://h10032.www1.hp.com/ctg/Manual/c06685332...
It gives you all the information you need about the different parts of the computer, as well as the replacement options available.
Feel free to ask if you have any other question !
Disclaimer: There are links to non-Microsoft websites. The pages appear to be providing accurate, safe information. Watch out for ads on the sites that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the sites before you decide to download and install it.