Maybe. It would be odd, though, not to find any Indian examples of zero from earlier than ~200 years after the oldest Khmer one if the invention came from India

Maybe. It would be odd, though, not to find any Indian examples of zero from earlier than ~200 years after the oldest Khmer one if the invention came from India. That area first came under Indian influence centuries before these dates. Some parts of the country, Chenla, were dependent on states in Java and Srivijaya (the one mentioned in the article) later on. The Indian cultural sphere as a whole covered a huge area and the Subcontinent itself certainly did not have a monopoly on culture there.