Here are a few rules about exponents you should know:
Firstly, multiply the y bases: [tex] \frac{z^5}{(-y^{-4}y^{-1}x^3)^{-3}}=\frac{z^5}{(-y^{-4+-1}x^3)^{-3}}=\frac{z^5}{(-y^{-5}x^3)^{-3}} [/tex]
Next, solve the power: [tex] \frac{z^5}{(-y^{-5}x^3)^{-3}}=\frac{z^5}{-y^{-5*-3}x^{3*-3}}=\frac{z^5}{-y^{15}x^{-9}} [/tex]
Finally, convert the negative exponent into a positive one and your final answer will be: [tex] -\frac{z^5x^9}{y^{15}} [/tex]