It's a fairly common way of bundling multiple files into one that has large support and usually "good enough" compression.

It's hardly revolutionary to do this, here are some common examples of things that are zip files but don't label themselves as such:

- .jar

- .odt, .ods, .odp, .docx, .xlsx, .pptx

- .epub

- .apk

- .crx, .xpi