（x+y+z）(x-y+z)+(y-x+z)(y-x-z)
=（x+y+z）(x-y+z)-(y-x+z)(x-y+z)
=((x+y+z）-(y-x+z)）(x-y+z)
=(2x）（x-y+z）
=2x(x-y+z)
如需请追问
如无请采纳!