Nikon Z5 has a
24.0MP Full frame (35.9 x 23.9 mm ) sized CMOS sensor and features Expeed 6 processor. On the other hand, Nikon Z7 has a
46.0MP Full frame (35.9 x 23.9 mm ) sized BSI-CMOS sensor and features Expeed 6 processor.
Nikon Z7's sensor provides 22MP more than Nikon Z5's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
One other difference between these two cameras that is worth mentioning is that Nikon Z7's sensor doesn't have an anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the Z5 and Z7 sensor size comparison.
Sensor Size and Resolution Comparison image of Nikon Z5 and Nikon Z7 Cameras
Nikon Z5 and Nikon Z7 have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Nikon Z5 has 88% larger pixel area compared to Nikon Z7, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Nikon Z5
or the
Nikon Z7 ,
including hyperfocal distance.