To switch between the different windows in the Inzomia viewer you double-click the titlebar of the window, the selected window will be enlarges while the other windows will scrink.
An image is loaded into the image window by doubleclicking its thumb in the playlist window. Try to double-click one of the images in your playlist. The image should load into the image window and the image window should be enlarged. Move the cursor to the image window, hold down the right mousebutton and move the cursor forward. This is the way to zoom in on a point in the image. To zoom out from the point keep the right mousebutton pressed and move the mouse toward you. Panning the image is done by holding the left mouse button while moving the cursor. Now double click the titlebar of this window to make it large again.