Version 0.6 is an early-access build. The game has since progressed much further (recent versions are in the 0.14+ range).
Since it is a .zip file, you need to right-click it and select "Extract All" or use a tool like 7-Zip/WinRAR. File: ProjektPassion-0.6-pc.zip ...
Based on the version number () and the suffix ( pc ), here is a quick breakdown of what this file usually is and how to handle it: What is Projekt Passion? Version 0