For starters make sure that you are following their supported matrix. http://s3.amazonaws.com/zertodownload_docs/Latest/Zerto%20Virtual%20Replication%20Operability%20Matrix.pdf?cb=1563315039
Failure to do so can result in your vra’s going offline.. Source = Lesson learned the hard way. I ended up having to recover 2 esx hosts back to the previous version