Panasonic ZS25 has a
16.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CMOS sensor . On the other hand, Panasonic ZS99 has a
20.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features Venus Engine processor.
Below you can see the ZS25 and ZS99 sensor size comparison.
Sensor Size and Resolution Comparison image of Panasonic ZS25 and Panasonic ZS99 Cameras
Panasonic ZS25 and Panasonic ZS99 have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Panasonic ZS25
or the
Panasonic ZS99 ,
including hyperfocal distance.