These are dangerous packages designed to look like a compressed archive (RAR or 7z) but actually contain malware. The Dangers of Highly Compressed Third-Party ISOs
Aside from the technical impossibility and security risks, there is the matter of legality. Microsoft owns the copyright to Windows 7. Distributing modified ISO files is a violation of copyright law. Download Windows 7 Highly Compressed In 10mb Iso File
You cannot go below ~400 MB without breaking Windows activation or core functionality. These are dangerous packages designed to look like