Nikon 1 V3 has a
18.0MP 1' (13.2 x 8.8 mm ) sized CMOS sensor and features Expeed 4A processor. On the other hand, Nikon Z50 has a
21.0MP APS-C (23.5 x 15.7 mm ) sized BSI-CMOS sensor and features Expeed 6 processor.
One other difference between these two cameras that is worth mentioning is that Nikon Z50'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 1 V3 and Z50 sensor size comparison.
As seen above, Nikon Z50 has a 3.2x Larger sensor area than Nikon 1 V3. 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.