What is the simplified form of -3z^2(z+2)-4(z^2+1)?

A. -7x^2 + 1
B. -3z^3 - 4z^2 - 6z - 4
C. -3z^3 - 2z^2 - 4
D. -3z^3 - 10z^2 - 4

The simplified form of -3z^2(z+2)-4(z^2+1) is -3z^3 - 10z^2 - 4. Therefore, the correct answer is D. -3z^3 - 10z^2 - 4.