Error durring the addition of a plugin

With projeqtor V6.0.8, when I add the plugin 'translationFrench' (Plug-ins->Plug-ins management->available plugins (local)->click on the button +)

I get the following error:
17-02-06 13:49:35.583 ===== TRACE ===== New plugin found : translationFrench_V1.2.zip
17-02-06 13:49:35.583 ***** ERROR ***** Impossible to load class ZipArchive<br/> => Not found in ../model/custom/ZipArchive.php <br/> => Not found in ../mod/ZipArchive.php <br/> => Not found in ../model/persistence/ZipArchive.php <br/>
17-02-06 13:49:35.583 ***** ERROR ***** EXCEPTION *****
17-02-06 13:49:35.583 ***** ERROR ***** on file '/var/www/projeqtor/model/Plugin.php' at line (431)
17-02-06 13:49:35.583 ***** ERROR ***** cause = Class 'ZipArchive' not found
17-02-06 13:49:35.583 ***** ERROR ***** => #0 /var/www/projeqtor/model/Plugin.php (65) -> getMetadata()
17-02-06 13:49:35.583 ***** ERROR ***** => #1 /var/www/projeqtor/plugin/loadPlugin.php (53) -> load()

Thank for your response.
This php extension is not mentionned into the readme.txt (PHP extensions required)
Could you update this file?

I had launch those commands on my server:
sudo apt-get install php7.0-zip
sudo service apache2 restart

But i get that error now:
2017-02-06 14:49:27.886 ===== TRACE ===== New plugin found : translationFrench_V1.2.zip
2017-02-06 14:49:27.887 ***** ERROR ***** ERROR *****
2017-02-06 14:49:27.887 ***** ERROR ***** on file '/var/www/projeqtor/model/Plugin.php' at line (66)
2017-02-06 14:49:27.887 ***** ERROR ***** cause = Undefined index: pluginVersion

Always the same...

I had launch that command on my server:
sudo wget -O /var/www/projeqtor/plugin/translationFrench_V1.2.zip 'www.projeqtor.net/plugins/vmcustom/downloadable/deliver_media
.php?uid=7039&pid=2'
After that, I went to the plugin page and I clicked on the add button.

But i got the same error :
17-02-08 09:32:50.488 ===== TRACE ===== New plugin found : translationFrench_V1.2.zip
17-02-08 09:32:50.504 ***** ERROR ***** ERROR *****
17-02-08 09:32:50.504 ***** ERROR ***** on file '/var/www/projeqtor/model/Plugin.php' at line (66)
17-02-08 09:32:50.504 ***** ERROR ***** cause = Undefined index: pluginVersion