What is the ruling on the muezzin raising his voice and attempting to prevent the designated Imam from leading the prayer, and what is the ruling on the Imam's statement to him: "What am I to do? Am I not the Imam?"?

The resident Imam has more right to lead the prayer than a visitor, even if the visitor is more knowledgeable in recitation and understanding of the Fiqh. Therefore, there is no blame on the resident Imam for leading the prayers even with the presence of a visitor. What the Muezzin did was a mistake and out of ignorance, and it is recommended to disregard the ignorant.