How is Zakat calculated for 2800 grams of commercial gold for the past six years in Egyptian Pounds, considering the fluctuating price of gold and not knowing the exact amount in past years, and is it permissible to pay it in installments if the amount is large?

The zakat on the gold left by the father must be paid for all the past years before his death, and the zakat is to be paid from the inheritance before its division. Zakat does not lapse due to the passage of time, and the heirs must exert effort in estimating the amount of gold owned by the father in past years, while seeking forgiveness for him and praying that Allah overlook his delay in paying zakat. Zakat is to be paid from the gold itself or from its current value at the price on the day of disbursement, and no consideration is given to the fluctuating value of gold. As for each heir's share, if their share reaches the nisaab and a full year has passed over it, then zakat is due on it.