To simplify this expression, we need to perform the operations in the following order: addition/subtraction, then division.

First, let's simplify the addition/subtraction inside each set of parentheses:

(-2/3 + 3/7) = (-14/21 + 9/21) = -5/21

(-1/3 + 4/7) = (-7/21 + 12/21) = 5/21

Now, let's simplify the division:

(-5/21) : (4/5) = (-5/21) * (5/4) = -25/84

(5/21) : (4/5) = (5/21) * (5/4) = 25/84

Finally, let's add the two results:

-25/84 + 25/84 = 0

Therefore, the simplified expression is 0.