To check if this extensions are enabled or not, you can create a php file i.e. info.php
and write the following code there:
<?php
echo "GD: ", extension_loaded('gd') ? 'OK' : 'MISSING', '<br>';
echo "XML: ", extension_loaded('xml') ? 'OK' : 'MISSING', '<br>';
echo "zip: ", extension_loaded('zip') ? 'OK' : 'MISSING', '<br>';
?>
That's it.