So, this Coolfire dragon in dragon city is quite hard to breed if you do not have a double flame dragon (which I don't have). And now it is required to participate in a battle in the frozen wind cup! Could somebody tell how to breed it?
In this link you can find some breeding options, most of which do not include the double flame dragon.
Next are Medieval and Alpine which have a 12.5% chance of getting cool fire.
You could also try Butterfly and Dandelion which have a 5.67% chance of getting cool fire.
You can get Butterfly with the login bonuses along with Double Flame which can basically solve your problem of not having one.