All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
The scholars hold differing opinions as to whether or not a Muslim may give the equivalent of the Zakah due on his money, such as the case in question. The majority of scholars are of the opinion that this is impermissible and it leaves the financial obligation on the giver unfulfilled. Some others regard this as permissible and valid. Still another group examines this issue in some detail, saying that if the equivalent of the due amount is given for no specific benefit, then it is not allowed. Yet, if it is given in this way to achieve some expected benefit for the poor, then it is allowable. This view is apparently closer to what is correct.
Hence, it is more proper to give the money due as Zakah to the poor who can spend it beneficially as they wish. In fact, they may be in more need of the money than a flat. Also, this is safer for the payer, given the consensus among scholars on the validity of paying Zakah in this way. However, if you want to follow the other approach, it should now have become clear to you that it is permissible when there is a desired benefit and a real need. But, there is a great difference between acting upon an opinion that is likely to be correct and another that is unanimously agreed upon.
Allaah Knows best.