Mailchimp Sync throws error after installing Hustle

Hi Gurus,

After installing Hustle, Mailchimp Sync is not working correctly. When I try to access Mailchimp Sync I get the following error:

Fatal error: Cannot redeclare class Mailchimp_Folders in /home/ecoevolv/public_html/growing/wp-content/plugins/mailchimp-sync/mailchimp-api/Mailchimp/Folders.php on line 3

If I have Mailchimp Sync Installed, why do I need to give Hustle my Mailchimp API key? doesn't make sense to me.

Anyway, what am I doing wrong here?

Thanks kindly,