Identify the type of irony in this example “ extremely moderate” hyperbole paradox understatement

I believe the answer is Paradox, since "extreme" and "moderate" are rather contradictory.
Hyperbole is an exaggerated statement or claim.
For an understatement, you need to know the context of the phrase before determining whether it truly is an understatement (I.e. something that is underestimated or under-represented).

Hope this helps! :)