Size and weight are big decision factors when you are trying to find the ideal camera for your needs.
In this section, we are going to illustrate the Panasonic ZS1 and Panasonic GF5 side-by-side from the front, back and top in their relative dimensions. Panasonic ZS1 has external dimensions of 103 x 60 x 33 mm (4.06 x 2.36 x 1.3″) and weighs 229 g (0.50 lb / 8.08 oz) (including batteries). Panasonic GF5 has external dimensions of 108 x 67 x 37 mm (4.25 x 2.64 x 1.46″) and weighs 267 g (0.59 lb / 9.42 oz) (including batteries).
Below you can see the front-view size comparison of the Panasonic ZS1 and the Panasonic GF5. Panasonic ZS1 is clearly the smaller of the two cameras. Its body is 5mm narrower, 7mm shorter and 4mm thinner than Panasonic GF5. As you can tell, actually this is not a fair size comparison since Panasonic ZS1 has a built-in lens but Panasonic GF5 doesn't. Once you put a lens on GF5, its thickness will increase significantly.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Panasonic ZS1 is significantly lighter (38g ) than the Panasonic GF5 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 GF5, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Panasonic Lumix DMC-ZS1 (Lumix DMC-TZ6) nor Panasonic Lumix DMC-GF5 provides any type of weather sealing in their bodies, 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 GF5's 3.00" LCD screen is slightly larger than Panasonic ZS1's 2.7" screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.