Compared to the crypto used in Zerocash, Zerocoin's internals are fairly elementary.
Zerocoin used one-way accumulators and discrete log based ZKPs, which are fairly approachable to anyone who has taken an undergraduate course in cryptography. Zerocash, however, uses Ben-Sasson's highly efficient zk-SNARK construct [0], the details of which are probably fully understood by a handful of people in the world. There's a reason the people who geek out over this kind of thing (#bitcoin-wizards) call it 'Moon math'.