Is it permissible to take from Zakat after one's financial situation deteriorates, or is it obligatory to sell land to cover expenses?

Paying Zakat to deserving relatives is better, unless they are among those whose maintenance is obligatory upon you, in which case it is not permissible to give them from Zakat. As for someone who owns wealth that suffices them, such as lands or properties, they must sell or rent them to meet their needs and the needs of those they support. It is not permissible for such a person to take Zakat because they are not among its rightful recipients, especially if they are capable of earning a livelihood.