What is the ruling on calculating usury, evaluating it, and recording it in accounting ledgers, and auditing it, knowing that this is an integral part of the work of external auditors for estimating the amount of Zakat?

It is not permissible to work in interest-based companies, because working with them is considered cooperation in sin and transgression. The Prophet (peace and blessings be upon him) "cursed the one who consumes Riba (interest), the one who pays it, the one who writes it down, and the two witnesses to it, and he said: they are all equal (in sin)."