If this Monster is another Zombie, the player shall receive a message but no other effects will occur. If this Monster is any other type, it will be "infected". Upon death, the body will Gib and an opponent that appears to be a Fiend will appear. This Monster is a seperate entity however, there is no death message or message for infection besides "Zombie infected".
While a separate entity, the newly created Monster shares all properties with a Fiend. Note Monsters can only be infected once, but after death can be infected once more as the newly spawned Fiend-like Monster is a separate entity.