documentclass{article}
usepackage[margin=0cm, top=0cm, bottom=0cm, outer=0cm, inner=0cm, landscape, a4paper]{geometry}
pagestyle{empty}
usepackage{tikz}

begin{document}
begin{tikzpicture}[overlay,remember picture]
pgfmathsetmacro{mywidth}{2*paperwidth/3-1cm} % kept local
node at ([xshift=-paperwidth/6-1cm]current page.center){%
    includegraphics[width=mywidth pt,height=paperheight]{example-image-a}};
    begin{scope}[x={(image.south east)},y={(image.north west)}]
        fill[even odd rule,opacity=0.4]
        (0.11,0.4) -- (0.37,0.404) --  (0.37,0.414) -- (0.11,0.41) -- cycle
        (0,0) rectangle (1,1);
    end{scope}
node at (current page.east){%
    includegraphics[width=mywidth pt,height=paperheight]{example-image-b}};
end{tikzpicture}
~
clearpage
begin{tikzpicture}[overlay,remember picture]
pgfmathsetmacro{mywidth}{2*paperwidth/3-1cm} % kept local
node (image) at ([xshift=paperwidth/6+1cm]current page.center){%
    includegraphics[width=mywidth pt,height=paperheight]{example-image-c}};
node at (current page.west){%
    includegraphics[width=mywidth pt,height=paperheight]{example-image-b}};
end{tikzpicture}
end{document}