Astronomy

Throughout the period of the Mayans, many of the Mayan people accomplished so many things.  A couple of these accomplishments include writing and math.  An accomplishment of writing is that scholars have called the Mayan writing one of the hallmarks of a true civilization.  My question is how were the scholars able to understand the writing of the Mayans?  I mean I could never understand the writing because it looks difficult to understand.  For the math concept, the Mayans were the first civilization to have the concept of zero.  This concept was a huge step in history.  I just don't understand how the Mayans were smart enough to establish all of the accomplishments that they accomplished.  This just amazes me!  Another idea that amazes me is the fact that they understood astronomy and how they created building that alined  with the stars.