I say, with Allah's guidance: If the debt has a claimant from the people, then he must deduct the amount of this debt from the money he has. If the money remaining after the debt reaches the nisab (minimum amount liable for zakat), then he must pay zakat on the surplus only; otherwise, there is no zakat on him. However, if there is no claimant from the people, such as vows, expiations, charity of breaking the fast, zakat debt, and the like, they do not prevent the obligation of zakat, and the amount of this debt is not deducted from the money he has, because their effect is in terms of the rulings of the Hereafter, which is the reward for fulfilling and sin for neglecting. As for the rulings of this world, they have no effect, as evidenced by the fact that he is neither compelled nor imprisoned for them, and Allah knows best.