I think it makes sense to break through both guards. That's what the teleport, or elevator, is for. If we follow your logic further, for example, in a situation with a four-way teleport on the map and guards positioned offset within it, it turns out that by breaking through one guard, you can immediately access three parts of the map. IMHO, that's absurd. As for the difference between multiple inter-zone guards and a teleport/elevator, when territories are located on the same plane, and there's only one guard between them (unless it's a so-called multiple passage), having several guards is more of an exception.