Since I am not a huge fan of cinnamon schnapps (with the exception of this drink and maybe a couple others), I never have any on hand. Two shooters will be plenty schnapps for a 6-pack of Zima. I have used Fireball as well in this. How much cinnamon liqueur is entirely up to the drinker. Experiment with the right amount for you.
1 bottle Zima
1/2 to 3/4 oz. Hot Damn! or Fireball or some other cinnamon schnapps-y type of liqueur
Fill a pint glass about 2/3 of the way with ice. Add the cinnamon liqueur and top off with the Zima.