Expiation for zihar, feeding sixty poor people: may ten be fed repeatedly?

Hisham said: Al-Hasan was asked about a man who owes the feeding of sixty poor people as the expiation for zihar; he feeds ten, then intends to feed those same ten again so that the sixty are completed (is that acceptable?). He said: "No, he must feed sixty poor people."

Something similar is reported from al-Sha'bi.