3) 6a - 6b 4c6 ⋅ c2 a²-b²;

3) $$\frac{6a-6b}{c^2} \cdot \frac{4c^6}{a^2-b^2} = \frac{6(a-b)}{c^2} \cdot \frac{4c^6}{(a-b)(a+b)} = \frac{6 \cdot 4 \cdot c^6 \cdot (a-b)}{c^2 \cdot (a-b) \cdot (a+b)} = \frac{24c^4}{a+b}$$

Ответ: $$\frac{24c^4}{a+b}$$