Size and weight is a big decision factor when you are trying to find the ideal camera for your needs.
In this section, We are going to illustrate Panasonic ZS7 and Olympus E-PL3 side-by-side from the front, back and top in their relative dimensions. Panasonic ZS7 has external dimensions of 103 x 60 x 33 mm (4.06 x 2.36 x 1.3″) and weighs 218 g (0.48 lb / 7.69 oz) (including batteries). Olympus E-PL3 has external dimensions of 110 x 64 x 37 mm (4.33 x 2.52 x 1.46″) and weighs 313 g (0.69 lb / 11.04 oz) (including batteries).
Below you can see the front view size comparison of Panasonic ZS7 and Olympus E-PL3. Panasonic ZS7 is clearly the smaller of the two cameras. Its body is 7mm narrower, 4mm shorter and 4mm thinner than Olympus E-PL3. As you can tell, actually this is not a fair size comparison since Panasonic ZS7 has a built-in lens but Olympus E-PL3 doesn't. Once you put a lens on E-PL3, its thickness will increase significantly.
Here is the back view size comparison of Panasonic ZS7 and Olympus E-PL3.
Now lets look at the top view comparison of Panasonic ZS7 and Olympus E-PL3.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Panasonic ZS7 is significantly lighter (95g ) than the Olympus E-PL3 which may become a big advantage especially on long walking trips.
Again, this comparison may not be very useful in real life as we are comparing the weight of a camera with a built-in lens to the body-only weight of an interchangeable lens camera. Once you put a lens on E-PL3, the total kit will weigh much higher.
Unfortunately neither Panasonic Lumix DMC-ZS7 (Lumix DMC-TZ10) nor Olympus PEN E-PL3 provides any type of weather sealing in their body, so you have to give extra care especially when you are shooting outdoors. If weather sealing is a must-have feature for you, check these sections: Top Compact Cameras with Weather Sealing Top Mirrorless Cameras with Weather Sealing
LCD Screen Size and Features
Panasonic ZS7 and Olympus E-PL3's LCD screens has the same diagonal size of 3".
On the other hand, Olympus E-PL3 features a Tilting screen
where you can change the angle of the screen to make it easier to shoot from waist or over the head levels whereas the Panasonic ZS7 has a fixed type screen which provides less flexibility in shooting positions compared to E-PL3.