Below you can see the front-view size comparison of the Panasonic FZ2500 and Olympus E-M5 II. The Olympus E-M5 II is clearly the smaller of the two cameras. Its body is 14 mm narrower, 17 mm shorter and 90 mm thinner than the Panasonic FZ2500.
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.