Is one discharged from the obligation of Zakat if the debtor pays it from his own money on behalf of the loan he owes, and then the owner of the money agrees to that?

The intention (niyyah) is a prerequisite for paying Zakat because it is an act of worship and an act of drawing closer to Allah. This is supported by legal texts, such as the Almighty's saying: "And they were not commanded except to worship Allah, [being] sincere to Him in religion," and the Prophet's (peace be upon him) saying: "Indeed, actions are by intentions." Zakat is not valid unless it is accompanied by intention. This is the view of the majority of scholars. Consequently, the Zakat paid by the debtor without the permission of the owner of the wealth is not sufficient, and the owner of the wealth must pay it again.