Pastrnak (1st round, 25th), Bergeron (2nd round, 45th), Krejci (3rd round, 63rd), and Marchand (3rd round, 71st) were all stars that were drafted by the Boston Bruins (none by Don Sweeney). They were drafted and developed, and all of them individually would cost far more draft/established personnel capital than the relatively low position the Bruins found them in.
One question to be asked is, was the old Bruins organization really lucky in finding these folks and getting hits in later rounds, or was part of it the skill of the development staff? In any event, trying to build a core without being good at the draft is really hard to do unless you have palm trees or casinos. We simply don't have the capital to do that. You have to play the draft game if you want to win the Stanley Cup.
The thing about Zacha is we don't have a first-line center. Zacha is what he is, a good but not game breaking 2nd line center. He'll get his cookies throughout the season, and he will be a serviceable 2nd line center. But, looking at the new guys coming up, there's some redundancy there with JH and Minten. It's all about who you think the core is. If you believe that the next wave players, such as Dean, Zellers, etc. are going to be the new Boston Bruins, then you need to start adjusting your window and converting assets for that core. We don't know what the return would be on Zacha, but you would have to listen, and you don't want to block your new core with aging assets. We have already seen our depth blocked and assets doing nothing in Providence.
I don't think you need to trade Pasta, but I think you should definitely be looking into trading Zacha and McAvoy