Complex sentence: A Dartmouth alumnus, he wants Zack to go to Dartmouth just like he did, and once made Zack wear a Dartmouth sweatshirt at just five years of age--an emblematic memory that causes Zack great annoyance for not being in charge of his own future.
Split into simpler sentences: A Dartmouth alumnus, he wants Zack to go to Dartmouth just like he did. He once made Zack wear a Dartmouth sweatshirt at just five years of age--an emblematic memory that causes Zack great annoyance about not being in charge of his own future.