None of the telephone screeners that will speak to you are in any way technical, so you will get away with showing them a wordpress site and passing it off as your own. What do you know about Zendesk? Can you explain what a trigger/macro/automation is? Explain a time you delivered great customer service? Explain a time you were under pressure? What is your career goals in the next 5 years? Any experience in HTML/CSS/Javascript? Any email experience? If you get through the telephone interview the next step is usually a demo of a part of the product. They are impressed if you go out and integrate say JIRA with Zendesk (pretty easy there is an article on their forum how to do it and its plug and play so no excuse for not spending an hour to get it done if you want the job). You will be expected to talk through it. If you get through that then usually you will have a skype or face to face with the team members. Here I cannot offer advice as the questions could be absolutely anything. Some people ask you tough questions and some just treat it like a casual chat in the pub.