If the Bruins are willing to move Lohrei for a #1C, it's going to have to be in a package. Lohrei on his own does not hold that value. The thing is, if the Bruins are going to empty their cupboards, it needs to be for an established #1C, Zegras in my opinion isn't that.
Regarding Lohrei, I think we can agree that the development path between defensemen and forwards is different. To me, Lohrei is an NHL defensemen who is great at transitioning the puck out of his zone and has the ability to contribute offensively. He definitely needs to flush out his defensive game more, but that will come with more experience and as he grows/bulks up.