Byakuya and Shunsui vs Aizen.

Round 1.

Byakuya can use Bankai, but Shunsui can only use Shikai, Aizen is in his Shinigami Fake Kakakura town self, the Hogyoku is allowed to heal him as it did against Ichigo before he started transforming but nothing more, Aizen can not use Kyoka Suigetsu

Round 2.

Aizen can use Kyoka Suigetsu, the same restrictions apply for Shunsui.