Panasonic ZS7 has a 12.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor and features Venus Engine HD II processor. On the other hand, Panasonic FH27 has a 16.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor and features Venus Engine VI processor.
Below you can see the ZS7 and FH27 sensor size comparison.
Panasonic ZS7 and Panasonic FH27 have sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Panasonic ZS7 has 32% larger pixel area compared to Panasonic FH27, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.