Panasonic S5 has a 24.0MP Full frame (35.6 x 23.8 mm ) sized CMOS sensor and features Venus Engine processor. On the other hand, Nikon Z6 has a 25.0MP Full frame (35.9 x 23.9 mm ) sized BSI-CMOS sensor and features Expeed 6 processor.
Another difference between these two cameras is that Panasonic S5's sensor lacks 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 moire occurring in certain scenes.
Below you can see the S5 and Z6 sensor size comparison.
Panasonic S5 and Nikon Z6 have almost the same sensor size so none of them has any significant advantage over other in providing control over depth of field when used with same focal length and aperture.