The wise Alice launches Antimagic Field on herself at the corner of Paladin Bob. Bob, not realizing this, goes around the corner and throws Zone of Truth over an area containing Alice.
Obviously, the effects of the Truth Zone are hanging around Alice, so she does not make any save rolls against the spell.
However, Truth Zone contains the following clause:
You know if each creature succeeds or fails their save throw.
What does Bob know about Alice 's success or failure of the coup de grace that she' s never done? Does he "know" that she "succeeded"? Or does he know anything, and so does he know that something has gone wrong with the fate due to his blatant lack of knowledge about Alice's backup?