BOOL pascal WinZoom(HWND hWnd)

  Maximizes a window, or restores a window to its previous size. The
maximize size for a window is the whole screen if the window is a
top-level window, or the size of its top-most ancestor's client area
if it's a child window. If a window is already maximized when
WinZoom() is called, then the window will be restored to its previous
size. There can only be one maximized window at one time.

Parameters
  hWnd is the handle of the window to maximize or restore.

Returns
  TRUE if the window was maximized or restores, FALSE if hWnd was an
invalid window handle or if the window did not have the WIN_MINMAXBOX
style.
.