Nikon today released two firmware updates.
The first is a bug fix update for the Z9, version 5.31. The sole item in this fix is a long-standing issue where the focus point might move from the subject in 3D-tracking and Subject-tracking AF. The earlier 5.3 update seemed to make this more likely to happen, and now it's been fixed, according to Nikon (I haven't had the chance to test it yet).
Meanwhile, the ZR got its first firmware update (to 1.10), with a number of modestly useful changes. Video can now be recorded for up to four hours, up to 50 LUT files can be added for View assist, file names can be given reel/clip/date and other information, timecode can be synced via the microphone/line input, and there are now warning indicators to indicate potential loss of detail in highlights when recording R3D raw files.