Simplifying
-4x4 + 4

Reorder the terms:
4 + -4x4

Factor out the Greatest Common Factor (GCF), '4'.
4(1 + -1x4)

Factor a difference between two squares.
4((1 + x2)(1 + -1x2))

Factor a difference between two squares.
4((1 + x2)((1 + x)(1 + -1x)))

Final result:
4(1 + x2)(1 + x)(1 + -1x)