Combat damage dealt by Haze Frog itself during the turn it enters isn't prevented. Combat damage that would be dealt by all other creatures is prevented, including creatures that weren't on the battlefield at the time the ability resolved.
2010-06-15
If two Haze Frogs enter during the same turn, each one's ability will prevent the other one's combat damage.
Flash (You may cast this spell any time you could cast an instant.)
When this creature enters, prevent all combat damage that other creatures would deal this turn.
