Simplify the following expression: (m-n)(m+n) / (m-m-m+n2) * n(n-m) / m(m+n)

The image shows a step in simplifying an algebraic expression. The expression in the image is: $\frac{(m-n)(m+n)}{m-mn-mn+n^2} \times \frac{n(n-m)}{m(m+n)}$ Based on the previous problem, the denominator of the first fraction was $m^2 - 2mn + n^2$. The term $m-mn-mn+n^2$ in the image appears to be a transcription error where $m^2$ was written as $m$. We will assume the intended denominator is $m^2 - 2mn + n^2$.

Step 1: Simplify the denominator of the first fraction. Assuming the denominator is $m^2 - mn