Below you can see the front view size comparison of Sigma Quattro H and Nikon Z6. Nikon Z6 is 13mm narrower and 23mm thinner than Sigma Quattro H but it is also 6mm taller.
Sigma Quattro H vs Nikon Z6 - Front View
Sigma Quattro H vs Nikon Z6 - Top View
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.
Camera Size Comparison
Select Two Cameras for Size Comparison