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.

35. Man has two inherent powers of will and understanding. When the understanding is governed by the will they then constitute one mind and so one life; for what a person in that case wills and does he also thinks and intends. But when the understanding is at variance with the will, as it is with people who claim to have faith and yet live otherwise, then a mind previously one is split in two. One half seeks to transport itself into heaven, while the other inclines towards hell. And because the will is what accomplishes everything, the whole man would rush straight into hell unless the Lord took pity on him.