Marriage With A Polytheist Is A Sin, But Still Valid?
Zabeeha relates to dietary matters. Haram Zabiha, unless its eaten, will stay Haram, but a sin is not committed as long as a Muslim refrains from eating that meat ( slaughtered by some other person ). As soon as the person eats it, a sin has been committed. It is also not a continued sin, and I hope no one would dare present the argument that since that meat becomes part of the body ultimately and will stay with him till that person dies, so that person is in a continued state of sin. You are using somewhat similar analogy about marriage. Eating non-Zabeeha meat and marrying a polytheist were both Haram for a Muslim. But once this violation is done, then it is of the same category i.e. a single violation of God’s directive.