Hostinger filemanger sucks!
It doesn't replace the old files with the new ones. (Which should be the standard behavior for any file manager)
On Hostinger, you will need to login into your SSH account (with IP, port, username, and password)
I would suggest using MobaXTerm
After you are logged in to your SSH, you will need to navigate to your domain's public_html directory and then extract the uploaded zip with: unzip YourZipName.zip
When it asks to replace all files, hit "A" and press enter.