I work with a 11" and a 12.9" iPadPro.
The Z5 RAWs are stored on a NAS station of the home network.
When I first opened the Z5 RAWs with the Files App, it was shown with a blank image on both iPadPro's with the image name and the words Nikon RAW.
I turned off the iPadPro. Not shut down.
After about 30...45 minutes I turned both iPadPro's on again. The Z5 RAW showed up correct in the Files app on both iPadPro. Transferring to Photos app with Share + Save did not work. Only a coarse pixelated photo is displayed.
However, opening in Pixelmator Pro or RAW Power works.