Is the construction of a project on the father's land contradictory to paying off his debt from Zakat, or must the land be sold to settle his debt?

It is permissible to give Zakat (definition) to a debtor if he is in hardship and cannot find a way to repay his debt, in excess of his basic needs. If he owns land that is not essential for his needs, the general principle is that it should be sold to repay his debt. However, if selling it would allow him to acquire another dwelling or another plot of land that meets his needs, and then have enough remaining to settle his debt, then he is obligated to do so. If the land is subject to legal disputes and cannot be sold, its existence is as good as its non-existence, and in that case, it is permissible to give Zakat to your father. But if it can be sold, then your father is not eligible for Zakat; either it must be sold, or his debt must be settled from a source other than Zakat.