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.

199. Internal Meaning of Joel, Chapter 2

1-2 The Lord will come and will execute judgment (1, 15)

2 when falsity and evil from the sensual has destroyed the whole church. (3)

4-9 Falsity of evil will destroy all things of it by various insanities. (3)

10 All good and truth has been dispersed, together with the knowledges [cognitiones] of them. (3)

11 The Lord will fight with them. (7)

12-17 Exhortation to be converted to Him, to repent, and to be wise. (2)

18-19 The Lord will establish the church, to which He will give its goods and truths, (11)

20 and will remove falsities of evil, and thus hell. (11, 17)

21-25 They will have trust in the Lord, from which they will have goods and felicities, (11)

26-27 and acknowledgment from the heart. (11)

28-29 By His Divine the Lord will fill those who are of that church with all things and will vivify them. (11, 12)

30-31 Falsities of evil and evils of falsity will dissipate influx on the day of judgment, (3, 15)

32 but those who acknowledge and worship the Lord will be saved. (17)