Why can't I open .zip files?

I've read in other discussions that this is an apparent bug.

Send Apple feedback. They won't answer, but at least will know there is a problem. If enough people send feedback, it may get the problem solved sooner.

Feedback

Or you can use your Apple ID to register with this site and go the Apple BugReporter. Supposedly you will get an answer if you submit feedback.

Feedback via Apple Developer

Use the free application "The Unarchiver." It's in the App Store.

You might try this: Open Activity Monitor (Utilities folder). Select "All Processes". Find the process called "appleeventsd". Select it and Force Quit it (with the quit button in the Activity Monitor window). Archive utility should run (if the bug mentioned by Eric Root is in play). The system will restart the (apparently buggy) process appleeventsd as needed.

Alternatively, restart.

charlie

This worked for me. Thanks CT.