What is the expiation for committing zina multiple times during the daytime in Ramadan, taking into account a legitimate excuse that prevents fasting due to medical treatment?

You must repent and make up the four days you broke your fast by intercourse in Ramadan. You are required to pay expiation for each day, which is fasting for two consecutive months. If you are unable to do so, you must feed sixty needy people for each day. As for your illness, if you can take the medicine twice a day (at Iftar and Suhoor), this does not prevent you from fasting. If you are unable to fast due to an illness from which recovery is expected, you can delay the expiation until you recover.