What is the method for paying zakat on a project involving the purchase of land and the construction of four villas for the purpose of sale and profit, knowing that one of the villas was sold for cash, another in installments, and two remain unsold, and no zakat has been paid on the money invested in the construction?

So long as the land was purchased with the intention of selling it, it is considered a trade commodity, and zakat (definition) is obligatory upon it. Each partner must pay zakat on his share if it reaches the nisab (definition) by itself or when combined with other funds, and a year has passed on it. This is done by giving out one-quarter of one-tenth (2.5%) of its value when the hawl (one year) is due, whether it has been built upon or not. The land and any existing structures are to be appraised. Zakat must be paid for every past year in which the share did not fall below the nisab. Zakat is not waived by prescription. If its price at that time is unknown, experts should be consulted to estimate it. Whoever's share does not reach the nisab is not required to pay zakat.