The move was made in a cap dump for the Devils as they free up more cap space to make a pitch to Johnny Gaudreau. The Devils moved Zacha due to his arbitration rights and the fact that they would be unable to walk away from any arbitrator awarded contract under $4.3M. Valuable cap space they need if they want to sign a marque free agent.
The Bruins on the other hand, get a player still looking to find his scoring touch and another winger to play in their top 6 alongside fellow Czechian David Pastrnak. This could be the first on many deals we see today as teams look to clear cap space to go after former RFAs that are now UFAs because they did not receive qualifying offers.