You have uploaded a zip file to your server with an FTP client but you can’t extract the zip file through the FTP client. This article helps you extract zip files using FTP client.
Step by step guide extract zip files through FTP client
Connect FTP client using username and password. Show any connecting error contact your WordPress hosting provider and ask them.
I am uploading the contact form zip file/wp-content/plugins/
folder in WordPress.

After uploading the contact form plugin zip file then upload the unzipper.php file. Download the unzipper zip file, and then extract the zip file on your computer. Please note, You need to upload the unzipper.php file to the folder where you upload the zip file.

Open your WordPress website. Open your WordPress plugin folder. The link will be like this
https://yourdomain.com/wp-content/plugins/unzipper.php
The unzipper page is open. If you extract the zip file current directory, leave the extraction path option blank. If not, write the extraction path. Then click the Unzip Archive button.

File unzipped successfully. After unzipping the contact form file delete the unzipper.php file.

In the same procedure, you can install plugin zip file in WordPress through FTP.
I hope this helped you learn to extract zip files using FTP clients. You can see my how-to category for more beginner’s guides.