Friggin Tree

Trees hate salt. Get a couple of containers of Morton's table salt and go to town with those roots. But make sure when the tree is dead it doesn't fall on your house. That would be your problem, not the neighbor's.

The tree is not within about 60 feet, and it’s only about 20-25 tall.
Biggest issue would be that it’s in reach of some of our cars at times.

Tordon22K is your friend, a few ounces of it around the base and the problem will be over. lol

That went in my phone as a reminder, thank you.
He would sooo notice the salt.