First I don't like Van Gundy one bit, however he was spot on with the Cs destroying the Heat's zone defense. So maybe Joe finally gets some credit for destroying Spo's coaching!
The Celtics played hard this series, and other than Game 2 they seemed well-prepared. Being ready and prepared is a big part of coaching, so for that Mazzulla deserves plenty of credit.
In terms of "destroying Spo's coaching", though... We're the best team in the NBA. Miami was in a 3-way tie for 16th. They were playing without Butler, Rozier, Richardson and at times Jacquez / Wright. What do you think Spoelstra -- or Popovich, or Red -- could have done to bridge that talent disparity?
That said, I do think the Celtics did a good job taking what Miami gave them. Particularly with Jacquez down, the Heat's defense didn't really have any good defenders outside of Bam. Not needing to cover KP any more, Spoelstra used Bam on Tatum. That impacted Tatum a bit early, but it also allowed the Celtics to draw Bam away from the paint. That made it a lot easier to get inside, even without our best inside presence. So, smart basketball.