If the .zip file is missing a "piece" to make it run (like a .dll or the RimWorldWin64.exe ), it’s usually because an antivirus program flagged and quarantined it.
It looks like you are referencing a specific archived version of (v1.4.3580). If you are looking for a "piece" in the context of a missing file, a mod, or a specific fix for that version, I can point you in the right direction depending on what you need. RimWorld.v1.4.3580.zip
Unless you need that exact build for a specific mod compatibility, the final stable version of 1.4 is . If the
Look in your Windows Defender or antivirus history. Unless you need that exact build for a
Since v1.4.3580 is an older sub-version of the 1.4 "Biotech" era, most mods labeled for should work. However, if you are looking for a specific "piece" of content: Steam Workshop: You can filter by version 1.4.