Is zakat obligatory on the remaining installments for the price of a house that was contracted to be purchased for the purpose of dwelling, knowing that I currently have the full remaining amount available?

You are allowed to deduct the apartment installments from your wealth. If, after deducting the installments, what remains reaches the nisab (definition) and a full lunar year (hawl) has passed over it, then zakat (definition) becomes obligatory on it, and its value is a quarter of a tenth. However, if you possess non-zakatable wealth that is surplus to your needs, then it should be used to cover the installment, and in this case, the installment should not be deducted from the principal wealth.