(x^+20xy+100y^2)z^2-16(x^2+20xy+1--y^2)
This is a foctoring problem! z^2 must be distributed and 16 must be distributed.
x^2z^2 + 20xyz^2 + 100 y^2z^2 - 16x^2 - 320xy + 16 - y^2z^2
now we combine any common terms. That means the variables are the same and of the same magnitude.
x^2z^2 + 20xyz^2 + 99y^2z^2 -16x^2 - 320xy + 16