Chemistry.
Zach doesn't understand the concept of romantic chemistry. In fact, it's a ridiculous term, he thinks to himself, for people who don't understand science. Although... chemistry is loud, messy, and explosive, which is not a bad description of some of his previous romantic attempts. There's also the quiet awkwardness of not understanding as someone who has a much more solid background in the matter stares at you, expecting you to know how to figure out the answer. With this too, he is familiar.
So Zach stares intot he corner and thinks he gets it a little more now. How it takes years of practice until it becomes second nature – how there's a whole new vocabulary, a whole new language to learn to speak and to read. How "organic" is a ridiculous word for something that comes so unnaturally to him. Pushing hair out of his eyes and refocusing on the patiently waiting computer screen, Zack straightens his posture and decides to work harder. There's an equation there that he can derive…or a theory, at least. Something testable in a lab.