Multiply or Divide $\frac{4 x-4 y}{21-7 z} \div \frac{2 y-2 x}{z-3}$

Multiply or divide.
- $\frac{4 x-4 y}{21-7 z} \div \frac{2 y-2 x}{z-3}$

A) $\frac{2}{7}$

B) $\frac{2}{21}$

C) $-\frac{2}{7}$

D) $\frac{2(x-y) }{7}$