Below you can see the front view size comparison of Nikon D5 and Pentax 645Z. Pentax 645Z is 4mm narrower and 42mm shorter than Nikon D5 but it is also 31mm thicker.
Nikon D5 vs Pentax 645Z - Front View
Nikon D5 vs Pentax 645Z - 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