y²-z²/z-y²

To simplify the expression \(\frac{y^2 - z^2}{z - y^2}\), we can start by recognizing that the numerator can be factored using the difference of squares:

\[ y^2 - z^2 = (y - z)(y + z) \]

The denominator is \(z - y^2\), which we can rewrite as \(-(y^2 - z)\):

\[ z - y^2 = -(y^2 - z) \]

Now we can rewrite the original expression:

\[ \frac{y^2 - z^2}{z - y^2} = \frac{(y - z)(y + z)}{-(y^2 - z)} \]

To simplify further, we can separate the negative sign from the denominator:

\[ = -\frac{(y - z)(y + z)}{y^2 - z} \]

This does not simplify nicely unless we have additional information about the relationship between \(y\) and \(z\). In its current form, the expression can be left as:

\[ -\frac{(y - z)(y + z)}{y^2 - z} \]

This is the simplified form of the expression based on the factoring and manipulation of terms. If there are specific values or further context, further simplifications may be possible.