Those who said: he prays Asr, then Zuhr

Al-Hasan said: "(If he has missed the Zuhr prayer,) he should first pray Asr and then Zuhr."

Tawus said: "If a man remembers during the Asr prayer that he has not prayed Zuhr, he should first complete the Asr prayer and then pray Zuhr."

Sayyiduna Ibn Umar (may Allah be pleased with them both) used to say: "If you remember during the Asr prayer that you have not prayed Zuhr, carry on with the Asr prayer, and after that pray Zuhr. And if, after praying Asr, you remember that you have not prayed Zuhr and then pray it, your prayer is valid."

The same is reported from al-Hasan.