Two-monitor display in ZPS X can be turned on by clicking the 
icon at the top right of the program window or pressing F10. When two-monitor display is turned on, a new program window appears on the second monitor. This window can be moved to any monitor. An arrow is displayed next to the icon; use this arrow to set which monitor displays the second window.
A 
icon is shown at the top right corner of the second window. Use this icon to hide the top panel, thus turning on fullscreen display.
The second window can display photos in the Browser and Preview modes. By default the Preview mode is active in the second window.