The suffix indicates this is a compressed archive.
You can usually find these files on the official CDC/NCHS website under the "ICD-10-CM" download archives. nchsk19zip 2021
The HSK level 19 is the highest level of the HSK test, indicating an advanced level of Chinese language proficiency. At this level, test-takers are expected to have a sophisticated understanding of Chinese grammar, vocabulary, and syntax. They should be able to comprehend complex texts, express themselves fluently, and engage in nuanced discussions. The suffix indicates this is a compressed archive