Does the Zakat that the father paid in advance from the joint account count as Zakat for the mother's money, given that the due date for Zakat was after his death?

Wealth transfers to the heirs upon the death of their inheritor. Zakat becomes obligatory on each heir if their share reaches the nisab (minimum threshold) and a hawl (one lunar year) passes over it. Zakat on money, gold, and silver does not differ whether combined or separated; what is obligatory is to give out a quarter of a tenth (2.5%) if the wealth reaches the nisab. If the father paid an advance Zakat on the shared wealth between him and his wife, one refers to his intention: Was the Zakat for his money alone, or the wife's money, or both their monies together? If he declared his intention, then it should be acted upon. Otherwise, it is apparent that he paid Zakat for all the shared wealth equally. Thus, the mother must pay the remaining Zakat due on her, which is half. And what the father paid as Zakat for his own wealth will be considered a voluntary charity for him.