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 Olympus E-M10 IV and Panasonic SZ1 side-by-side from the front, back and top in their relative dimensions. Olympus E-M10 IV has external dimensions of 122 x 84 x 49 mm (4.8 x 3.31 x 1.93″) and weighs 383 g (0.84 lb / 13.51 oz) (including batteries). Panasonic SZ1 has external dimensions of 99 x 59 x 21 mm (3.9 x 2.32 x 0.83″) and weighs 131 g (0.29 lb / 4.62 oz) (including batteries).
Below you can see the front view size comparison of Olympus E-M10 IV and Panasonic SZ1. Panasonic SZ1 is clearly the smaller of the two cameras. Its body is 23mm narrower, 25mm shorter and 28mm thinner than Olympus E-M10 IV. As you can tell, actually this is not a fair size comparison since Panasonic SZ1 has a built-in lens but Olympus E-M10 IV doesn't. Once you put a lens on E-M10 IV, its thickness will increase significantly.
Here is the back view size comparison of Olympus E-M10 IV and Panasonic SZ1.
Now lets look at the top view comparison of Olympus E-M10 IV and Panasonic SZ1.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Panasonic SZ1 is significantly lighter (252g ) than the Olympus E-M10 IV 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-M10 IV, the total kit will weigh much higher.
Unfortunately neither Olympus OM-D E-M10 IV nor Panasonic Lumix DMC-SZ1 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 Mirrorless Cameras with Weather Sealing Top Compact Cameras with Weather Sealing
LCD Screen Size and Features
Olympus E-M10 IV and Panasonic SZ1's LCD screens has the same diagonal size of 3.00".
On the other hand, Olympus E-M10 IV 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 SZ1 has a fixed type screen which provides less flexibility in shooting positions compared to E-M10 IV.