I haven't found a way to maximize a hidden window; being "zoomed" and "withdrawn" are both considered "states" by Tk, and apparently a window cannot be in both states simultaneously.

An alternative is, when zooming the height:

1. save the current window position and size
2. maximize the current window
3. set the horizontal position and width to their original values

There is a visual artifact when doing so - the window is seen to maximize and then return to its original width.