2/x=3/y=4/z
z=2x y=3x/2
(4x²+2yz+z²)/(x+y+z)×(x-y-z)/(8x²+4yz+2z²)
=(4x²+6x²+4x²)/(7x/2)×(-5x/2)/(8x²+12x²+8x²)
=4x×(-5/56x)
=-5/14