Is it permissible for a student of knowledge who is eligible for Zakat to work voluntarily on a non-profit religious project, and be given from Zakat funds to settle his debts and needs, with the knowledge of the Zakat payers?

The poor person who is given Zakat (definition) is one who is unable to earn a living. If a person is poor or indebted and unable to earn a living, there is no harm in giving him Zakat, whether he works on a project or not. It is not permissible to stipulate that he works on a charitable project in exchange for Zakat; because compensation for Zakat funds is not permissible. If he is unable to earn a living, his needs are met from Zakat without the condition of work. If he is able to earn a living, it is not permissible to give him Zakat.