Only use ditto to extract skipped volumes.

Library/Homebrew/extend/os/mac/unpack_strategy/zip.rb

@@ -1,9 +1,28 @@
 module UnpackStrategy
   class Zip
+    prepend Module.new {
       def extract_to_dir(unpack_dir, basename:, verbose:)
+        volumes = super.stderr.chomp
+                       .split("\n")
+                       .map { |l| l[/\A   skipping: (.+)  volume label\Z/, 1] }
+                       .compact
+
+        return if volumes.empty?
+
+        Dir.mktmpdir do |tmp_unpack_dir|
+          tmp_unpack_dir = Pathname(tmp_unpack_dir)
+
           # `ditto` keeps Finder attributes intact and does not skip volume labels
           # like `unzip` does, which can prevent disk images from being unzipped.
-      system_command! "ditto", args: ["-x", "-k", path, unpack_dir]
+          system_command! "ditto",
+                          args: ["-x", "-k", path, tmp_unpack_dir],
+                          verbose: verbose
+
+          volumes.each do |volume|
+            FileUtils.mv tmp_unpack_dir/volume, unpack_dir/volume, verbose: verbose
           end
         end
+      end
+    }
+  end
 end

Library/Homebrew/unpack_strategy/zip.rb

@@ -18,7 +18,8 @@ module UnpackStrategy
       quiet_flags = verbose ? [] : ["-qq"]
       system_command! "unzip",
                       args: [*quiet_flags, path, "-d", unpack_dir],
-                      verbose: verbose
+                      verbose: verbose,
+                      print_stderr: false
     end
   end
 end