Both Nikon Z5 and Leica TL2 have 24.0 MP resolution sensors but Nikon Z5's sensor is Full frame (35.9 x 23.9 mm ) and Leica TL2's sensor is APS-C (23.6 x 15.7 mm ).
Since Nikon Z5's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Leica TL2.
Below you can see the Z5 and sensor size comparison.
As seen above, Nikon Z5 has a 2.3x Larger sensor area than Leica TL2. 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.