The opposite sides of a rectangle will always be congruent. If they aren't, it's not a rectangle.
To find CD, you need to find what z is. This can be found using the given, the perimeter, and plugging that into the perimeter formula using the information given. You end up with 2(4z - 3) + 2(3z - 1) = 132. Solve for z and you find that z = 10.
CD is congruent to AB, which is 3z -1. Plug z in to get AB = 29. Since AB = CD, CD = 29.