Tried to cure a zombie villager with a splash instant health potion but the zombie was not effected and could not feed it a golden apple. Tried to cure a zombie villager in creative mode and this did not work either. If multiple potions are used the Zombie villager just takes damage from the potion and eventually dies.
Cannot reproduce, even in older versions. The proper way to cure a zombie villager is to use a splash potion of weakness, not an instant health potion as the zombie villager could get hurt, and then feed it a golden apple. I will close this issue as invalid as it cannot be reproduced.