Now get ready for a shocker: you entered a "No Suit" zone capture with the "Eternal Zombie". The reason you could still keep it equipped is because the suit name doesn't contain the word "Suit", and the reason you couldn't unequip it was because the bind you were probably pressing was a bind of an actual suit, such as an ACS, which it won't let you unequip because you aren't allowed to use that type of suit in that zone capture if you were pressing an "Eternal Zombie" bind you would of been fine