My "Donald Tr... eh, Duck" size comparison with the Z7.
I used the diametre of the shutter button to adjust size to "close enough".
Although they say final looks might be different, on the Z9-alleged photo I can see dedicated ISO and BKT buttons, and the usual flash cable and 10-pin cable connections, portrait mode dials and shooting button. Still no info on top ISO and pixel count, I'll assume twin memory card slots, exposure times up to 900 secs, and maybe the orientable rear screen...
BTW, practically same size as a Z7+extra grip (which is -alas- lacking the portrait mode buttons)
Ciao from Massimo