Brandon, Zachary and Ben all are tenors. Zachary has too much ease in his upper chest range to be a baritone also his low notes arent full and resonant like a baritone.
About Zachary, yes he has ease in his upper register, but his voice is too rich and masculine, much more than Jeremy Jordan, Ben Platt, etc. to be a true tenor.
We can agree to disagree :) Not all tenors sound the same. And not all tenors have thin bright voices. I'm actually speaking from experience. There are rich and big/full tenor voices (me included). Also, his vocal cords usually haven't come together all the way on his low notes in recordings I've heard. That also is a clue he is not a baritone.