Praise be to Allah.
What this man has done is haraam for two reasons:
He has asked for something additional to the loan. It is not permissible to take something additional to a loan or to benefit from the loan, because it is a contract that is based on kindness, seeking thereby reward. So it is not permissible for the lender to take from the borrower something that is additional to the loan, or to impose any obligation on him or to stipulate anything for him, because this is riba, and in fact it is the worst kind of riba. The Prophet (blessings and peace of Allaah be upon him) said: “Every loan that brings a benefit is riba.” Even though there is some debate concerning the soundness of this hadeeth, the scholars are unanimously agreed on this point, that the lender is not permitted to benefit from the wealth of the borrower because of the loan.
So what this man has done is riba, and he has to repent to Allaah and return this additional amount that he took from you and imposed on you.
The zakaah on wealth is only due from the owner, not from anyone else. The fact that he forced you to pay zakaah does not mean that his duty has been discharged, because zakaah is due from the one to whom the debt is owed, and he is required to pay it. End quote.
Al-Muntaqa min Fataawa al-Shaykh Saalih al-Fawzaan (2/304)