How is Zakat calculated on money after receiving annual profits from shares purchased in a commercial company for the purpose of benefiting from their annual yield, and how is Zakat calculated on the questioner's share from the sale of a building after three years and eight months of ownership?

Commercial offerings are subject to zakat (definition) on the principal capital and its profit upon the completion of a year, not on the profit alone. Therefore, the zakat for the cement company shares from previous years must be paid by calculating their value each year and giving 2.5% of it.

Similarly, the land you bought with the intention of building and selling is considered a commercial offering, and your share in it must be zakat-ed annually at 2.5% of its value for each of the past three years, whether its value increased or decreased, provided it does not fall below the nisab (definition).