I think it would be better to say they are two christian denominations (χριστιανικά δόγματα).

When will the new tree come out?

No, they aren't different religions, but different forms of Christianity according the Wikipedia, https://en.m.wikipedia.org/wiki/Eastern_Orthodox_Church and https://en.m.wikipedia.org/wiki/Protestantism . I think it is a non-biased term that doesn't not uses the term "heresy", as this term is so much charged, from the Ancient verb αίρω, a different dogma, that separated from the mainstream. https://el.m.wiktionary.org/wiki/αίρεση

could 'creed' translate θρησκεία?

Grammatically correct but factually incorrect sentence.