: Unlike ZIP, it is not native to Windows or macOS and requires third-party tools like the official 7-Zip or PeaZip . 7z file you already have? Multilingual Dataset Combiner/Cleaner - Mozilla Discourse

One prominent "long post" involving es.7z is found on the forum. It discusses a Multilingual Dataset Combiner/Cleaner used for training DeepSpeech models.

: It uses the LZMA and LZMA2 algorithms, which can provide 30–70% better compression than standard ZIP files.