What is the ruling on going to a man who claims to heal with the presence of Muslim jinn, and asks for the names of the mother, father, and grandmother, to diagnose sorcery and treat with Zamzam water?

This man is a sorcerer and a charlatan. The proof of this is that he asks for the name of your mother's mother and her father, and these are questions that only sorcerers and charlatans ask. A legitimate raqi (one who performs ruqya) does not need such questions. We advise you to stay away from him and not to use him in your mother's treatment, for it is authentically reported from the Prophet, peace and blessings be upon him, that he said: "Whoever goes to a kahin (soothsayer) or an arraf (diviner) and believes what he says, has disbelieved in what was revealed to Muhammad, peace and blessings be upon him." And his saying about al-Nushra (a magical cure for magic): "It is from the work of Satan." Al-Nushra is of two types: solving magic with magic, which is from the work of Satan, and solving magic with ruqya, incantations, and permissible medicines, which is permissible. Seek medicine for your mother through legitimate means from doctors or through legitimate ruqya from those known for their righteousness, and by reciting Surat Al-Baqarah in the home and upon your mother.