z4a−2 + z4a−4 + z3a−1 + z3a−3−4z2a−2−4z2a−4−3za−1−3za−3 + 5a−2 + 3a−4 + 3 + 2a−1z−1 + 2a−3z−1−2a−2z−2−a−4z−2−z−2