You can change the size of the 3D View window to make it larger or smaller.
How to do
From your Zakeke back-office go to Settings > Interface Editor > Actions > check the "3D View" Window's size flag.
You have to set the width and the height in pixels. Please note that the window does not change in the preview mode, always check the live version of your customizer.
If you want to restore the default size of the 3D view, you only need to uncheck the "3D View" Window's size flag.