Should I pay again the zakat on money that I spent to purchase a medical device for a governmental hospital for the poor, and should I pay it immediately or wait until the next Hawl (Zakat year) is due?

It is not permissible to purchase medical equipment with Zakat funds, even if the beneficiaries are poor, because Zakat cannot be used to buy weapons or real estate to be endowed for the sake of Allah. Therefore, the obligation has not been fulfilled, and the Zakat must be disbursed immediately without delay.