Canon M3 has a 24.0MP APS-C (22.3 x 14.9 mm ) sized CMOS sensor and features DIGIC 6 processor. On the other hand, Nikon Z30 has a 21.0MP APS-C (23.5 x 15.7 mm ) sized CMOS sensor and features Expeed 6 processor.
One other difference between these two cameras that is worth mentioning is that Nikon Z30'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 M3 and Z30 sensor size comparison.
As seen above, Nikon Z30 has a 1.1x Larger sensor area than Canon M3. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.