Simplify. \[ \frac{z^{6} y^{3}}{z^{6} y^{4}} \]

To simplify the expression \( \frac{z^{6} y^{3}}{z^{6} y^{4}} \), we can divide the numerator and the denominator by \( z^{6} \) since they are the same in both places: \[ \frac{z^{6} y^{3}}{z^{6} y^{4}} = \frac{y^{3}}{y^{4}}. \] Next, we can simplify \( \frac{y^{3}}{y^{4}} \) using the property of exponents that states \( \frac{a^m}{a^n} = a^{m-n} \): \[ \frac{y^{3}}{y^{4}} = y^{3-4} = y^{-1}. \] Thus, the simplified expression is: \[ y^{-1} = \frac{1}{y}. \] So the final answer is: \[ \frac{1}{y}. \]