Image link:
https://gyazo.com/97aa24f74c9679cfb14da53f7c6da645
This image shows a bunch of hands. You can see Zach's and his hand on Pappas's chest.
There is not much in it. But the refs can't process what happened with a high degree of accuracy in real-time. Zach runs in with intent. Places not much of hand on Pappas. Pappas goes down and almost loses his shirt, which makes it looks worse than it is.
Honestly, I can see how the refs came to sending Zach off. Albeit not much in it, the evidence would have looked to the ref that it was worse than it is.
But who knows how Pappas stays on the park? Just an awful decision. The tackle was disgusting.