(2x-3y+z)-3{x-2[-z+(x-y)]-(3y-5z)}
=(2x-3y+z)-3[x-2(-z+x-y)-3y+5z]
=2x-3y+z-3(x+2z-2x+2y-3y+5z)
=2x-3y+z-3(-x-y+7z)
=2x-3y+z+3x+3y-21z
=5x-20z