I really am having an EXTREMELY tough time wrapping my head around the chain rule... i have the problem (-3x^2-4)^4(8x^2+4)^-8

Here is what I did

4(-3x^2-4)^3(-6x)(8x^2+4)^-8 + (-3x^2-4)^4(-8)(8x^2+4)^-9(16x)

=-24x(-3x^2-4)^3(8x^2+4)^-8 - 128x(3x^2-4)^4(8x^2+4)^-9

and thats all i got and i dont know what to do next