The answer is \(-\frac{ z^{4} }{2}\)
\(\frac{4 z^{a+2} }{-8 z^{a-2} } = \frac{4}{-8} * \frac{z^{a+2} }{ z^{a-2} } =- \frac{1}{2} *\frac{z^{a+2} }{ z^{a-2} } \\ \\ \frac{x ^{a} }{ x^{b} } = x^{a-b} \\ \\
- \frac{1}{2} *\frac{z^{a+2} }{ z^{a-2} } =- \frac{1}{2} * z^{a + 2 - (a - 2)} =- \frac{1}{2} * z^{a + 2 - a + 2} =- \frac{1}{2} * z^{4} = -\frac{ z^{4} }{2}\)
