Must zakat be paid or given for the days the deceased father did not fast, having died in an accident on the 6th of Ramadan?

If a person dies in Ramadan (definition) after having made up for missed fasts, nothing is required of him for the remaining days, as religious obligations cease upon death.

As for one who dies while owing fasts from Ramadan: 1. If he died before it was possible to make up the fasts (due to lack of time or an excuse), then most scholars hold that nothing is incumbent upon him. 2. If he died after it was possible to make up the fasts, then the majority of scholars hold that it is obligatory to feed a poor person for each day he owed. Abu Thawr dissented, saying that fasts should be observed on his behalf.

The majority of scholars adduced as evidence narrations indicating the obligation of feeding, such as the hadith (definition) of Ibn Umar: "Whoever dies while owing a month's fasts, a poor person should be fed for each day in his stead." They did not differentiate between making up for Ramadan fasts and a vowed fast, except for the Hanbalis, who said that fasts should be observed on his behalf for a vowed fast.

Therefore, if your father owed fasts from Ramadan and died having been negligent in making them up, you must feed a poor person a mudd for each day he owed. Nothing is required for the rest of the month in which he died.