$12-{\left( {\left( -2 \right)}^{2}-4 \right)}^{3}$
Evaluate the power$12-{\left( 4-4 \right)}^{3}$
The sum of two opposites equals $0$$12-{0}^{3}$
$0$ raised to any positive power equals $0$$12-0$
Removing $0$ doesn't change the value, so remove it from the expression$12$