Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
Intending to perform two good deeds by one act is possible in some acts like Hajj and Umrah or Ghusl and Wudu. But it is not possible in other acts including fasting. So, you cannot have two intentions for fasting one day.
From the above you know that you have to redo the expiation fasting of that day and make up for the day of vow (Nadhr).
Allah knows best.