Respuesta :

[(x − 8y) + z] * [(x − 8y) − z]

= (x − 8y)² - z²  
[ Following the rule: a² - b² = (a + b)(a - b) where 'a' here is (x − 8y) and 'b' is z ]

= x² -16xy +64y² - z²

= x² + 64y² - z² - 16xy