Phone screening that was set up my my employee referral, followup phone interview with team manager, then on to in person interview with two Zendesk employees. What's cool is they were transparent the whole time (most notably the team manager stage) and she let me know during that conversation that she was passing my through to the next stage.

Typical call screening followed by an interview with the hiring manager. If they like you they then pass you on to a series of 4 interviews and a mock EBR. Pretty standard process.