[Kikasso]

вроде так работает:

var XS  =  ( x1 >= x0 ) === ( x0 >= x2 );
var XS2 =  ( x3 >= x0 ) === ( x0 >= x4 );
var YS  =  ( y1 >= y0 ) === ( y0 >= y2 );
var YS2 =  ( y3 >= y0 ) === ( y0 >= y4 );

upd: исправил, спасибо Futs