Ruling on zakah on a debt – should it be paid from other wealth?

Firstly: 

The scholars of the Standing Committee said: 

If the debtor is in difficulty or he has sufficient funds but he is taking a long time to pay back the loan, and the lender cannot get his money back from him – either because he does not have proof that will help him get it back through the authorities or he has proof but he cannot find any authority figure to help him get his rights – as happens in some countries where there is no support for people’s rights – then the lender does not have to pay zakah until he gets his money back and one full hijri year has passed since he got it. 

But if the debtor has sufficient funds and it is possible to get the money back from him, then the lender has to pay zakah every time a full hijri year has passed, if the loan reaches the nisaab by itself or when added to other money, etc.

Fatawa al-Lajnah al-Daa’imah li’l-Buhooth al-‘Ilmiyyah wa’l-Ifta, 9/191 

Secondly: 

If zakah is due on a person’s wealth, it is not permissible for him to dispose of it except in the ways prescribed in sharee’ah, which are explained in the answer to question no. 6977. It is not permissible to use zakah to feed the fasting or to establish a charitable waqf, because these are not among the eight areas in which zakah is to be spent, as defined by Allaah, may He be exalted. 

We have already explained that it is not permissible to use zakah funds to build mosques and schools, or to print Mus-hafs. See questions no. 13734 and 21797. 

And Allaah knows best.