difference of squares formula:
a^2 – b^2 = (a + b)(a – b)
so answers are
(3 + xz)(–3 + xz)
(y2 – xy)(y2 + xy)
(64y2 + x2)(–x2 + 64y2)
cause
(3 + xz)(–3 + xz)
= (xz + 3 )(xz - 3)
= x^2z^2 - 9
--------------
(y^2 – xy)(y^2 + xy)
= y^4 -x^2y^2
----------
(64y^2 + x^2)(–x2 + 64y^2)
=(64y^2 + x2)(64 - x^2)
= 64^2 y^4 - x^4