A:
If the case is as you have mentioned, then
Zakah is due on the share of each heir if the value of this share reaches the Nisab (minimum amount upon which Zakah is due) as long as they had the intention to sell the land. The amount of the due Zakah must be calculated after the elapse of a Hawl (one lunar year calculated from the time a property reaches the minimum amount upon which Zakah is due). Thus, whenever a Hawl passes from the time they intended to sell it, Zakah must be calculated and each heir must pay Zakah on their share, if it reaches the Nisab either on its own or by adding the share to his personal wealth, be it cash or goods. If some of the heirs intended to offer their share in the land for sale while the rest did not, then the ruling applies only to those who intended to sell.May Allah grant us success. May Peace and Blessings of Allah be upon our Prophet Muhammad, his family and his Companions!