How to open / extract .DMG on Windows

First get yourself a copy of 7-zip as installed or portable version dose not mater. Than open the .DMG with 7-zip an extract the 2.hfs file.

Extract what you are looking for

After you have extracted the 2.hfs file open it with 7-zip and find the content you looking for in this example a .IPSW file.

Extract what you are looking for