WP Smuch Pro will not activiate

I get the following error when I try to activate WP Smush Pro

Fatal error: Cannot redeclare wp_smush_rating_message() (previously declared in /home4/ab89831/public_html/wp-content/plugins/wp-smushit/wp-smush.php:73) in /home4/ab89831/public_html/wp-content/plugins/wp-smush-pro/wp-smush.php on line 88