Extension Upgrade Failed: Download failed - ZIP file is unavailable or malformed
You could do a manual upgrade:


download the zipfile from https://civicrm.org/extensions/civirules 
remove the civirules directory from your extension folder on the server
extract the downloaded zip file
upload the org.civicoop.civirules folder to your extension folder on the server
Go to the extension page in civicrm and see whether any database upgrades are reuired.


ps. It is a good habit to make a backup before step 1.