Well, that depends by what you want and your skills.
I have seen your post on xentax where you asked how to open unyakuza.c and so I'm aware that you have zero skills, which means that if you want a complete solution (like a rebuilder tool) you are lost.
Technically for the lzss-like algorithms it's very easy to create a fake recompression function, for example a byte 0x00 followed by 8 original bytes, but that's completely useless in your situation because you have to recreate all the file (sllz) or archive (par) format.
quickbms has a very useful reimporting feature that can be used with the existent script IF someone is able (and has time) to write a REAL recompression function.
In that case you can post on https://encode.ru
asking if someone wants to do the job and when I will have the recompression function I will implement it in the next quickbms version, but it's very important that the recompressed data is smaller/equal than the original compressed data (that's why the fake recompressor can't be used in quickbms).
Just for curiosity, are you really sure that the game needs the dds compressed as sllz?
If yes can you post a couple of these sllz files?
The fake recompressor may be used to create the sllz files but no way to use it with the par archives due to all the structure that must be created.