Modern software is all about interoperability and eliminating data silos, according to ZenPayroll founder Joshua Reeves. Today the founder and his company are putting their money where their mouth is, launching a payroll API that could allow their software to create a more connected back office. And with more than $150 million in annual payroll flowing through ZenPayroll today — that’s up 50 percent in the last two months — the news has the potential to make a big splash.