35 points
*
You’re not missing much. A few modern file types are zips with expected folder structures, especially MSOffice files. But this is nowhere near universally true.
You can open a file in your text editor of choice and if you see it start with PK (for Phil Katz the creator of the format and the original PKZIP/PKUNZIP programs) then it’s probably a zip.
Also, by the logic of the OP, all DLLs are EXEs.
