The hallow and unhallow spells cancel each other by overlapping.
Does this mean the attached spell (e.g. silence) is canceled as well?
It explicitly states the land is still both hallowed and unhallowed, and doesn't suggest that anything happens to their spell effects (if it does, that's very, very unclear). For that matter, a body in such an area can still not be turned into an undead creature, since the hallowed area effects are still in play.