I have a friend who is divorced. Is he permitted to have relations with a non-Jew?
Would the answer be different if Jewish woman (single/divorced) had relations with a non-Jewish man?
Answer:
It is not permitted for a Jewish person to engage in marital relations with non-Jews.
This prohibition applies both for a Jewish man and non-Jewish woman, and vice versa (see Avodah Zarah 36b, where a distinction is made between cohabiting within the framework of a marriage, which is more severe than a one-time act). See Rambam (Hilchos Issurei Biah Chap. 12).
If the cohabitation is public, the transgression is far more severe, but it is possible that this extra severity applies specifically to a Jewish man and non-Jewish woman.
Best wishes.
