Senior Member
I would rather group the Z6 / Z7 family in a different way:
Z6 and Z7 in one group
Z6 II and Z7 II on one group
Z6 III alone in a third group.
because the cameras in the two first groups, the cameras in these groups differs almost nothing from each other, Z6 and Z7 are nearly identical, apart from the resolution, Z6II and Z7II are in the same manner almost identical, but Z6III is an entirely new camera, with specs far away from it's previous siblings.