Is it permissible to delay paying Zakat on an amount designated as a down payment for purchasing an apartment, knowing that the purchase date is after the Zakat due date (Hawl)? And is it considered a debt that can be paid when the money becomes available due to outstanding installments?

Whoever is obligated to pay zakat (definition) must disburse it immediately. It is not permissible for him to delay it if he is able to, because it is a right of the poor, and this is the view of the majority of scholars. A Muslim must hasten to pay zakat, for it does not decrease wealth but rather purifies and increases it, in accordance with the Almighty's saying: {Take, [O, Muhammad], from their wealth a charity by which you purify them and cause them increase}, and the saying of the Messenger of Allah, peace and blessings be upon him: "Charity does not decrease wealth."