What if a lot of mythologies fight?

I'm writing a book of fantasy but highly inspired by mythology
The primary mythologies are japonese myhtology, norse, greek, egyptian and roman
Each of them have to fight with other mythologies (persian, hindu, budism, mesopotamian, aztec, maya, inca, celtic, babylonian, chinese and maybe arturian), you can suggest others
Selecting of that what of this mythologies you would put against one of the five until a max of 3
Example: Greek against babylonian, hindu and aztec