az7−a3z5 + 4az5−2z5a−1−3a3z3 + 7az3−5z3a−1 + z3a−3 + a5z−5a3z + 7az−4za−1 + za−3 + a5z−1−3a3z−1 + 4az−1−2a−1z−1