This is not shopped. Heh. It is in fact a zorse. The white coloring/spots comes from the fact that the horse parent was a Paint/Pinto, specifically a Tobiano. That means the horse has white splotches all over its coat and on all four legs. A tobiano pinto can be mostly white or more evenly colored. As for why the zebra stripes are only expressed in the non-white portions, I'm not really sure, but I suspect it has something to do with the pinto coloration covering them up along with the base color.