I was contacted by one of Zendesk's design heads and proceeded onto a screen with HR, multiple rounds of group and one-on-one interviews, as well as a design test. Most interviews took place via Skype/Hangouts and involved a broad range of people from the company, including a founder. There was also an on-site interview with 3 groups of 2-3 people. It's nice to know that Zendesk really care about the recruitment process and are looking for the right people to join the team.