Also look up 7zz on linux/macOS, fixes #9951

src/Composer/Command/DiagnoseCommand.php

@@ -177,12 +177,18 @@ EOT
 
         $finder = new ExecutableFinder;
         $hasSystemUnzip = (bool) $finder->find('unzip');
-        $hasSystem7zip = (bool) $finder->find('7z', null, array('C:\Program Files\7-Zip'));
+        $bin7zip = '';
+        if ($hasSystem7zip = (bool) $finder->find('7z', null, array('C:\Program Files\7-Zip'))) {
+            $bin7zip = '7z';
+        }
+        if (!Platform::isWindows() && !$hasSystem7zip && $hasSystem7zip = (bool) $finder->find('7zz')) {
+            $bin7zip = '7zz';
+        }
 
         $io->write(
             'zip: ' . (extension_loaded('zip') ? '<comment>extension present</comment>' : '<comment>extension not loaded</comment>')
             . ', ' . ($hasSystemUnzip ? '<comment>unzip present</comment>' : '<comment>unzip not available</comment>')
-            . ', ' . ($hasSystem7zip ? '<comment>7-Zip present</comment>' : '<comment>7-Zip not available</comment>')
+            . ', ' . ($hasSystem7zip ? '<comment>7-Zip present ('.$bin7zip.')</comment>' : '<comment>7-Zip not available</comment>')
         );
 
         return $this->exitCode;

src/Composer/Downloader/ZipDownloader.php

@@ -49,6 +49,9 @@ class ZipDownloader extends ArchiveDownloader
             if (!Platform::isWindows() && ($cmd = $finder->find('7z'))) { // 7z linux/macOS support is only used if unzip is not present
                 self::$unzipCommands[] = array('7z', ProcessExecutor::escape($cmd).' x -bb0 -y %s -o%s');
             }
+            if (!Platform::isWindows() && ($cmd = $finder->find('7zz'))) { // 7zz linux/macOS support is only used if unzip is not present
+                self::$unzipCommands[] = array('7zz', ProcessExecutor::escape($cmd).' x -bb0 -y %s -o%s');
+            }
         }
 
         if (null === self::$hasZipArchive) {