Panasonic ZS3 has a 10.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor . On the other hand, Panasonic GH2 has a 16.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor and features Venus Engine FHD processor.
Panasonic GH2's sensor provides 6MP more than Panasonic ZS3's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the ZS3 and GH2 sensor size comparison.
![Panasonic ZS3 vs Panasonic GH2 Sensor Size Comparison]()
Sensor Size and Resolution Comparison image of Panasonic ZS3 and Panasonic GH2 Cameras
As seen above, Panasonic GH2 has a 8.1x Larger sensor area than Panasonic ZS3. 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.