Zooming changes the size of shapes. E.g. a circle turns into a slight oval as the zoom factor is not 100%, 200%, 300%, or 400%.
When you create a shape and change the zoom factor it appears that height and width vary. This makes it difficult to create exact graphics.
Also, when the angle is not 0°, the zoom factor changes the position of shapes. When two shapes at say 45° are exactly in line with 100% zoom, they are changeing to steps at different zoom factors.