I am trying to find nonzero prime ideals of \mathbb{Z} \oplus \mathbb {Z}, specifically those which are not also maximal.
If I try to do direct sums of prime ideals, the resulting set is not a prime ideal. (e.g., 2 \mathbb{Z} \oplus 3 \mathbb{Z} is not prime since (3,3) \cdot (2,2) = (6,6)\in...