The Archmage NPC casts Mind Blank on itself before entering combat per the MM. Mind Blank is powerful enough to foil a Wish spell to gain information about or affect the mind of a target, per the PH.
How does this affect a Zone of Truth spell? Would the Mind Blanked creature have to make a saving throw? Would the Zone of Truth caster be aware of a failed save? Would the Mind Blanked creature be aware of the Zone of Truth?