Better use zstd version "1.3.7", as it is stored in trine5.exe.
Although it doesn't make any sense, I looked through some of the streams in the texture archives.
Code:
#1 174760 > 174752 = 8 bytes
#2 349520 > 349504 = 16 bytes
#3 11184808 > 11184800 = 8 bytes
#4 5592400 > 5592384 = 16 bytes
#5 699048 > 699040 = 8 bytes
#6 1398096 > 1398080 = 16 bytes
#7 43688 > 43680 = 8 bytes
#8 22369616 > 22369600 = 16 bytes
Actually this is the repeating size pattern.
Code:
Signature(1),DSize(4),Unknown(8),ZstdHdr(4),Stream
This Unknown 8 bytes are actually the byte size difference for DSize. 8 and 16.