To factor $ 4m^3+12-cm^3-3c $ we can use factoring by grouping.
Group $ \color{blue}{ 4m^3 }$ with $ \color{blue}{ 12 }$ and $ \color{red}{ -cm^3 }$ with $ \color{red}{ -3c }$ then factor each group.
$$ \begin{aligned} 4m^3+12-cm^3-3c &= ( \color{blue}{ 4m^3+12 } ) + ( \color{red}{ -cm^3-3c }) = \\ &= \color{blue}{ 4( m^3+3 )} \color{red}{ -c( m^3+3 ) } = \\ &= (4-c)(m^3+3) \end{aligned} $$