Panasonic FZ60 has a 16.0MP 1/2.33" (6.08 x 4.56 mm ) sized CMOS sensor . On the other hand, Sony RX10 IV has a 20.0MP 1" (13.2 x 8.8 mm ) sized BSI-CMOS sensor and features Bionz X processor.
Below you can see the FZ60 and RX10 IV sensor size comparison.
As seen above, Sony RX10 IV has a 4.2x Larger sensor area than Panasonic FZ60. 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.