Решение:
\[ \frac{z^2-8z+16}{z^2-16} = \frac{(z-4)^2}{(z-4)(z+4)} = \frac{z-4}{z+4} \]
\[ \frac{z-4}{z+4} = \frac{-16-4}{-16+4} = \frac{-20}{-12} = \frac{5}{3} \]
Ответ: 5/3