>> The Zoom app notifies Facebook when the user opens the app, details on the user's device such as the model, the time zone and city they are connecting from, which phone carrier they are using, __and a unique advertiser identifier__ created by the user's device which companies can use to target a user with advertisements
IDFA is the same across all apps on a device. However, it can be reset by the user or disabled (in which case it returns all 0s). Also, apps have to disclose (to Apple) that they use the IDFA - not sure if that's visible to the user in the App Store anywhere.
IDFV is unique per vendor - that is, each app has a different ID, but two apps from the same developer will have the same ID. I believe this is also reset when resetting the device.
The FBSDK doesn't require developers to enable the IDFA, so the unique identifier in the phone home request is either the IDFV (effectively unique) or just a UUID that the FBSDK generates and stores on launch.