You had to know this was coming. Since the movie is out in some places, and there's already been a few threads with Shazam *mumblemumbleIhatecallinghimthatmumblemumble*, let's get this one out of the way.
Win by KO
Thor has Stormbreaker, of course
Shazam has full knowledge of his powers
Fight takes place on Peter Jackson's Hobbit/LOTR Middle Earth where the Five Armies fought (neutral territory)