Is it permissible for a husband to have intercourse with his wife on a night that is not hers, but rather the night of her co-wife?

It is forbidden for the husband to enter upon any wife other than the one whose night it is, and intercourse is forbidden as a matter of even greater priority. This ruling applies whether his work is during the day and her assigned night is at night, or vice versa. Imam Ibn Hajar Al-Haytami in "Al-Tuhfa" made an exception for entering due to necessity, such as a frightening illness of the wife. If his stay then is prolonged, he must make up for it; otherwise, not.