Does Zakat become obligatory on an amount of 200,000 EGP that has completed a full year (hawl), given that I have real estate debts amounting to 350,000 EGP, and are these debts to be deducted from the amount subject to Zakat?

Scholars have differed on deducting debt from zakat. The more cautious approach is not to deduct it, which is the newer opinion of Ash-Shafi'i and the preferred view of Ibn Baz and Ibn 'Uthaymeen.

However, according to the opinion that debt can be deducted (which is the preferred view on this website): If you have surplus assets beyond your needs (such as real estate), then allocate them to cover the debt, and pay zakat on the full amount without deducting the debt's value. If you do not have surplus assets, then deduct the remaining debt and pay zakat on what remains, provided it does not fall below the nisab.

And should one deduct the entire debt or only the installment due? The more cautious approach is to deduct only the installment due.