Below you can see the front-view size comparison of the Panasonic ZS100 and Olympus E-M10 III. The Panasonic ZS100 is clearly the smaller of the two cameras. Its body is 11mm narrower, 19 mm shorter and 6 mm thinner than the Olympus E-M10 III.
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.