For the problem on the left, the 2 capacitors are parallel to each other so the 1/z = 1/-2j + 1/-2j = 2/-2j
so 1/z = 1/-j = -1/j
so the total impedance of the 2 capacitors, z = -j
Now if you add this to 5j + 4 (the total impedance of the resistor and inductor) you get 4j+4. However this doesn't give the right answer..