This plugin will add a reCaptcha to all Zoo comment forms. You can also change the look of the reCaptcha, just select one of the four different themes. And it is also possible to log all reCaptcha attempts and IP addresses.
After a submission the user gets redirected to the comment form where also all messages are displayed conveniently. Without the plugin Zoo would display the message at the top (very inconvenient ...)
Configuration is easy, just enable the plugin from Menu -> Extensions -> Plugin Manager and enter your public and private key that you received from reCaptcha (see also use reCAPTCHA on your site)