Earliest time after Heraclius' death the Roman Empire could have begun to expand again?

Historically, the Byzantines were only really able to start gaining territory again in the 10th and early 11th centuries, and that was quickly undone after the Battle of Manzikert. Were there opportunities for Roman reconquests before this?

Perhaps attacking the Abbasids during the Zanj Rebellion?
 
Probably around the time of Constantine V, if the Caliphate fractured due to a civil war. External factors are the major constraint, methinks. The Roman Empire could have basically expanded whenever the enemy was weak after the plague ended in mid eighth century, and possibly even earlier.
 
Probably around the time of Constantine V, if the Caliphate fractured due to a civil war. External factors are the major constraint, methinks. The Roman Empire could have basically expanded whenever the enemy was weak after the plague ended in mid eighth century, and possibly even earlier.

But the Byzantines didn't do much during the Abbasid Revolution or the Zanj Rebellion, both of which fractured the Caliphate.
 
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