Extra Screen?

I pressed shift+z and now have an extra screen which I can’t seem to get rid of…
any help would be appreciated; thanks!

not a lot to go on…

Throwing it out the window generally helps, but watch out for passers-by.

Shift z was added to provide a shortcut for rendered view in cycles, but I (and many others I believe) had already made some other shortcut for it, Alt X for me …so I’m only guessing that’s what the question was about. . But anyway the OP has closed Blender and reopened it and has the default screens back and is blissfully moving on.