It took a little longer than expected, but Zotero has now accepted the updated stylesheets for the McGill Guide 10th Edition - available now in both English and French versions. Quick link is here: Zotero Style Repository.
You can still download the stylesheets from this site (blog post: McGill Guide 10th Edition stylesheets for Zotero!) including example Word documents. However, you can simply add the styles from within Zotero directly!
A big thank you to the open source community that contributes and maintains Zotero!