Animate Dead in a zone affected by Hallow?

Question

The hallow spell prevents undead from entering a certain area:

First, celestials, elementals, fey, fiends, and undead can’t enter the area, nor can such creatures charm, frighten, or possess creatures within it. Any creature charmed, frightened, or possessed by such a creature is no longer charmed, frightened, or possessed upon entering the area. You can exclude one or more of those types of creatures from this effect.

In addition, it has an optional effect to prevent dead bodies interred within from becoming undead:

Everlasting Rest. Dead bodies interred in the area can’t be turned into undead.

Assuming the caster of hallow did not select the Everlasting Rest option, if a character casts animate dead on a corpse within a hallow zone, what happens to the resulting zombie or skeleton?

Answer 1

Animate dead functions as usual, but the undead cannot reenter if they leave.

You correctly observe that preventing the creation of undead creatures is an optional feature of the spell hallow. So animate dead will function as expected, the hallow spell does not prevent it unless the caster chooses the Everlasting Rest feature of the spell when it is cast.

When the undead is raised, they can move and act as normal. The only restrictions on them in the spell description are:

undead can't enter the area, nor can such creatures charm, frighten, or possess creatures within it.

If they are already in the area, they cannot properly enter the area, but if they leave the affected area, they would not be able to enter it again.