Joby Franczek

BFG Tools – Theme Zipper lets you quickly create portable .zip files of any installed theme, including child themes.
Use it when you want to:
<ul>
<li>Move a theme from one site to another.</li>
<li>Send a theme to a developer or client.</li>
<li>Create a safe, portable copy of a customized child theme.</li>
</ul>
All zips are stored in your WordPress uploads folder under <code>/wp-content/uploads/theme-zips</code> and can be downloaded directly from the Theme Zipper page.

BFG Tools – Theme Zipper

Zip any installed WordPress theme (including child themes) from Tools → Theme Zipper. Zips are saved in /wp-content/uploads/theme-zips.

Aaron Jorbin

A workaround for users who are dealing with improperly created zip files.

Force PclZip

Force the use of PclZip instead of ZipArchive

BFG Tools – Theme Zipper vs Force PclZip