Zorder of windows on dual monitors

Question

The z-order of a window indicates the window's position in a stack of overlapping windows.

If you work with dual monitors, does each monitor have it's own z-order?

Answer 1

No. Having separate Z-orders per monitor would make it difficult to get reasonable results when moving windows between monitors, or when windows overlapped multiple monitors. There is a single desktop-wide Z-order.

Answer 2

No. It's possible that a window may exist on both monitors simultaneously, so the z-order is for the entire desktop.