We can use distribution property to multiply the polynomial by the monomial.
$$ \begin{aligned} \left( -3x^2+3 \right) \cdot \left( \color{orangered}{-2x^2} \right) &= \left( -3x^2\right) \cdot \color{orangered}{-2x^2} + 3 \cdot \color{orangered}{-2x^2} = \\ &= 6x^4-6x^2 \end{aligned} $$