The tool is optimized for decompression.

LZ4 is symmetric: it compresses about as fast as it decompresses. That suits logs and swap, but not data that is shipped. A firmware image is compressed once on a build server and decompressed on every device that installs it, so time saved during compression helps nobody.

ZXC moves the work to the encoder. Match selection, optimal parsing and statistics tuning are done once, and the bitstream is laid out for the pipelines and branch predictors of modern processors. The decoder stays short, has few branches, and uses SIMD where it is available.