The piglin, and the zombified piglin it turned into exists at the same time for a brief moment when a piglin is zombified.

You can see this by waiting until a baby piglin tursn zombified right when it's running. This may take a while to succeed. 

Video(I was using vanilla, I forgot to display the F3 debug screen) : https://www.youtube.com/watch?v=9QAtbC0eoEA