How is Zakat paid on 15,000 placed in an investment portfolio within a project affiliated with the Islamic Bank, which stipulates profit and loss, and cannot be withdrawn before two years, knowing that its hawl (one year) will be completed three months from now?

You must pay zakat on the aforementioned amount as long as it has reached the nisab at the completion of a full year (hawl). It is not a condition that you pay zakat from the exact amount itself. If another year passes and there is a profit, then zakat is obligatory on the original amount and its profit.