Is it permissible to pay Zakat in monthly installments, and to what extent is this permissible in cases where one is able or unable to pay it in a lump sum?

It is not permissible to delay Zakat after it becomes due, unless it is impossible for the payer to disburse it due to a reason beyond their control, based on the Almighty's saying: "Allah does not burden a soul beyond its capacity." In such a case, they must strive to disburse it as soon as possible.