The given expression is:

(x-2)^3 - (x+2)^3

Expanding using the formula for the difference of cubes:

= (x^3 - 3x^22 + 3x2^2 - 2^3) - (x^3 + 3x^22 + 3x2^2 + 2^3)
= x^3 - 6x^2 + 12x - 8 - x^3 - 6x^2 - 12x - 8
= -12x^2 - 16

Now expanding the second expression:

(ab - 3a^3 + 9)(a^3 + 3) - a^9
= a^4b + 3ab - 3a^6 - 9a^3 + 9a^3 + 27 - a^9
= a^4b + 3ab - 3a^6 - a^9 + 27

Therefore, the simplified expression is:

-12x^2 - 16 + a^4b + 3ab - 3a^6 - a^9 + 27