The second use of Satan refers to the demons that serve Satan. AT: "If Satan works against his own demons" (See: [[rc://en/ta/man/translate/figs-metonymy]])
Jesus uses this question to show the Pharisees that what they were saying was illogical. AT: "If Satan were divided against himself, his kingdom would not be able to stand!" or "If Satan were to fight against his own demons, his kingdom would not last!" (See: [[rc://en/ta/man/translate/figs-rquestion]])