The observation that the author made about the philosophical development of the idea of nothingness (shunyata) leading to the development of the zero (shunya) i

The observation that the author made about the philosophical development of the idea of nothingness (shunyata) leading to the development of the zero (shunya) is very key. You can't have the latter without the former. In Indic thought, it is common to talk about a set of items and then the null set - 1 pen, 2 pens, 3 pens and then no-pens or the absence of pens. This notion of the absence of something can be roughly translated as shunyata. Symbolically and cardinally that idea got translated to zero.