I've worked with Camunda extensively, which Zeebe is based on.

I've found Camunda to be incredible. The APIs are implemented well and the work flow processing paradigm is easy to work with. Setting up the Camunda engine as a web server in a Spring project and integrating with external sources is great.

I've found there can be some performance issues when running a single engine, but clustering is easily enabled and you can adjust with a dedicated worker paradigm too.

Great piece of tech honestly. Haven't worked with Zeebe yet but am excited to.