In a case where a Cohen wishes to marry a woman regarded as a "zona", does Halacha provide any possibility for the Cohen to voluntarily forfeit his status as a Cohen in order to proceed with the marriage?
If you are fortunate enough to be a cohen, you cannot renounce or forfeit it. Like Judaism, it’s an inborn privilege, which I personally would love to have! You are a member of a unique family, the only one in the world that can trace its lineage back 3,300 years, a tribe so full of life and holiness, that you shouldn’t come into contact with death nor unholy relationships. The reason that this virtue is irreversible is because only someone who is ignorant about the priesthood would dream of leaving this great status, so G-d does them a favor and basically "forces" them to discover their good fortune! Like a kingly loving father, who wants to give his son a great gift, but his son isn't mature or learned enough to realize why this gift is so great- the loving father will not give his son any choice, but keeps the gift waiting until the son learns to understand. Welcome Back! Rav Ari Shvat