`a) 2(x-y)(x+y)+(x+y)^2+(x-y)^2`
`=2(x^2-y^2)+x^2+2xy+y^2+x^2-2xy+y^2`
`=2x^2-2y^2+x^2+y^2+x^2+y^2`
`=4x^2`
`b) (x-y+z)^2+(z-y)^2+2(x-y+z)(y-z)`
`=(x-y+z)^2+2(x-y+z)(y-z)+(z-y)^2`
`=(x-y+z).(x-y+z+2y-2z)+(z-y)^2`
`=(x-y+z)(x+y-z)+(z-y)^2`
`=[x+(z-y)].[x-(z-y)]+(z-y)^2`
`=x^2-(z-y)^2+(z-y)^2`
`=x^2`