Does deferred debt prevent Zakat from being due on saved amounts that exceed the installment of the debt due in the year of Zakat, especially if these amounts represent part of the value of an asset whose ownership increases with increased payments, and which carries an element of growth or trade?

Zakat (definition) may not be obligatory on wealth itself. If a man owns real estate and cars and does not intend them for trade, then there is no Zakat on them. As for debt, the majority of scholars are of the opinion that it prevents Zakat on internal wealth (gold, silver, currency, trade goods) under certain conditions. If the debtor does not own what covers his debt, then there is no Zakat on him for the mentioned amount, and he is not obliged to take on debt to pay Zakat. However, buying houses with the intention of selling them when their price increases is subject to Zakat, and this is called trade goods.