Not necessarily true, still can be saved if exposed skeleton is not too much, can try coral dipping it in coral rx or lugol solution to help healing a few times in the next few weeks. Regular WC will help too.
Zoanthids already opened up nicely. Should be ok, juz keep a close watch on your water parameters & do weekly or fortnightly WC should be gd enough to keep your water clean and replenish elements in it.