Zoom in / Zoom out

I want to have two glyphs open at the same time and compare their apperance next to each other.
How can I make sure that the zoom in both windows matches? I couldn’t find a “zoom factor” function.

Their is a zoom field next to the + and - maginfiying glasses. You can enter a value there, or you can click on fit to window. The zoom factor will be the same with fit to window unless you resize them. Tile vertically will make them the same size. You can also modify the default zoom for the glyph edit window from Tools, Options.

Another way is to use the comparison toolbar, and display the other character before or after the current glyph in a single glyph edit window.