Elle.7z

: Ideal for archiving large sets of similar binary files where space is at a premium.

Solid compression is most effective when you are archiving a large number of very similar files, such as multiple versions of a document or software backups. Instead of compressing each file individually, 7-Zip looks for redundancies across all files in the "solid block." Elle.7z

7-Zip / Discussion / Help: 7-zIp And Compression Noob - SourceForge : Ideal for archiving large sets of similar

: Increasing the number of threads to match your CPU's logical processors can speed up the compression process, though it may slightly increase the final archive size. Elle.7z