I wouldn’t pay much attention to just one other persons Unverified Personal Gnosis (UPG).
If a couple of people here or elsewhere that you trust, independently verify something similar, the it’s plausible, otherwise, UPG is UPG. 
That would be against the rules on this forum, as it comes under “preaching”. Generally if you want to be taken seriously, just talk about your direct experiences, your UPG. Others will say if they have experienced differently.
I don’t really know why a Greek and a Norse pantheon entity would have anything to do with each other, why they should “fight” or why it matters. It’s their business, no? Is this some sort of human pissing context going on? Unless this was a case of being cursed and a patron deity helping the target…? 
Magick is subjective so this is probably not going to help you 
… See UPG.
What you want to do, I suggest, is go evoke the deities in question and ask them yourself. Get your own UPG going on, and rely on that.
Always believe yourself first. Because what’s true for you isn’t always true for others. Never just take other people’s UPG at face value.
Yes, and it’s the will of the practitioner that matters, not the entities in question or what you call them.
You are the magick one reaching out, giving permission and energy for a magickal act, your expectations and fears make a massive difference.