Zendesk is good to those who doesn't know much about it, cuz when you get to know more about the product, you know how their customer support sucks.
They are quick at charging, and shutting down accounts, but yes, takes months to solve minimal issues.
For basic questions, their customer support will send you HC links.
For complicated questions, they customer support CAN ONLY send you HC links too.
So you better have no complicated questions to ask if you are going to choose Zendesk. Cuz they don't have customer support for complicated issues.