Is it permissible to deduct the difference between the profits of a deposit in a usurious bank (10%) and an Islamic bank (7%) from zakat on money?

It is not permissible to count the difference in usurious interest as part of zakat, because zakat is a right for the deserving and it is not permissible for the zakat payer to benefit from it. Furthermore, usurious interest must be disposed of by spending it on charitable causes with the intention of getting rid of unlawful money, not with the intention of charity.