Is zakat obligatory on a sum of money saved to buy land, which is temporarily invested in purchasing shares to increase it?

Zakat is obligatory on money designated for purchasing land for building and residential purposes if it reaches the nisab (minimum threshold) and a full hawl (lunar year) passes over it, whether the money is saved or invested in stocks. However, if the land is purchased before the completion of the hawl, then there is no Zakat due on it.