Are the Muʿtazilah condemned to hellfire because they are deviant sects, based on the Ḥadīth of the splitting of the Ummah, and does this apply to Al-Zamakhsharī?

It cannot be definitively stated that the Mu'tazila will enter Hell, but rather they are judged to be among the misguided sects. As At-Tahawi concluded his creed by disavowing those who contradicted what he mentioned, and As-Saffarini stated that the Mu'tazila are one of the roots of the people of innovation (Ahl al-Bid'a), and that they comprise twenty sects, all characterized by innovation and misguidance. No individual among them can be definitively said to enter Hell except with a specific text.