8(a-b)^3 + 27
= (2a-2b)^3 + 3^3
= (2a-2b+3)((2a-2b)^2 - (2a-2b)3 + 3^2)
= (2a - 2b - 3)(4a^2 - 4ab + 4b^2 - 6a + 6b + 9)