In Ezekiel 26:11, this signifies the love of learning or intellectual things. (Arcana Coelestia 3727)

In Revelation 6:2, this signifies the love of understanding the Word. (Apocalypse Revealed 298)

In Zechariah 12:4, this signifies that the intellectual should be filled with falsities. (Arcana Coelestia 2383[2])

In general, 'a horse' signifies knowledge or understanding of the Word. In an opposite sense it signifies the understanding of the Word falsified by reasonings, and likewise destroyed from self-derived intelligence. 'A dead horse' signifies no understanding of truth from the Word.

209. No influx is possible from the lower into the higher heavens because this is contrary to order, but there is influx from the higher heavens into the lower. Also the wisdom of the angels of a higher heaven surpasses the wisdom of the angels of a lower heaven, as a myriad to one. This is another reason that the angels of a lower heaven cannot speak with those of a higher heaven. In fact when they look towards them, they do not see them, the higher heaven appearing like a mist over their heads. Angels of a higher heaven, however, can see those in a lower heaven, but they are not allowed to talk with them on pain of losing their wisdom, as has been said above.