How do I disconnect my google calendar from ZOHO?

How do I disconnect my google calendar from ZOHO?

My Google calendar is being affected by ZOHO. My appointments are suddenly disappearing, and ZOHO is sending me emails nearly every 10 mins to remind me about my appointments and wont stop. Also, when I am in ZOHO, pop up windows appear to remind me about calendar appointments and won't go away even after I click the [X] or click "OK", and if the box doesn't go away it does not allow me to use ZOHO.

Help! How do I disconnect my google calendar from ZOHO?