Well, just type "zero maya number" into any search engine and click on "pictures". The most common symbol for zero in the Late Postclassic codices was a stylised shell, but in Classic period inscriptions, more complex "notational" or "head-glyph variants" are used.

Southern Mesoamerica's mathematical system - which logically requires the zero value - must have been developed during the first millenium BCE, but due to the lack of early inscriptions on perishable materials, all we can say for sure is that it was fully operational by the first century BCE. And, of course, that it was an independent invention.