Let's simplify the expression step by step.

8a - 8b / b * (1/a + b - 1/a - b)

First, let's simplify the expression within the parentheses:

1/a + b - 1/a - b = (1/a - 1/a) + (b - b) = 0 + 0 = 0

Now we have:

8a - 8b / b * 0

Since anything multiplied by 0 is 0, the entire expression simplifies to 0.