Let's simplify the expression step by step:

Distribute the negative sign in the expression: -(3-c)(3+c)
= -3(3) - 3(c) + c(3) - c(c)
= -9 - 3c + 3c - c^2
= -9 - c^2

Substitute this simplified expression back into the original expression:
3 - c(3-c) - (-9 - c^2)
= 3 - (3c - c^2) + 9 + c^2
= 3 - 3c + c^2 + 9 + c^2
= 12 - 3c + 2c^2

Therefore, the simplified form of the expression is 12 - 3c + 2c^2.