Is it permissible to purchase an "undetermined land receipt" regarding its location and area, and to benefit from it through a Sharia-compliant agency (wikala shar'iyya) to dispose of the land later while it remains in the seller's name, and is Zakat obligatory on this receipt?

Selling this land is impermissible for two reasons: The first is the ignorance of its location and area. Among the conditions of sale is the absence of ignorance regarding the sold item or the price. The second is that its owner has not yet acquired possession of it, and selling what one does not possess is impermissible. There is no zakat due on the receipt, because zakat on trade goods is only obligatory for what is intended for commerce, and the sale of this is not permissible.