The latest firmware update for Nikon Z-series cameras allows them to use CFexpress, a new memory-card format associated with faster transfers compared to XQD. This new software also allows the Z 6 or Z 7 to record 4K UHD or full-HD video in RAW. However, this can only be done with Atomos recorders and may not be available for free.
https://www.notebookcheck.net/Nikon-updates-the-Z-7-and-Z-6-with-CFexpress-card-and-RAW-video-output-support.447911.0.html