From my understanding of ancient numbering systems, zero was a late invention. What was so hard about the concept? Wasn’t it obvious that sometimes you had nothing?
Sua.
Zero as a concept (as in, “Yes, I have zero bananas”) wasn’t difficult.
Zero as a place-holder in determining numbers, that was the deep step. Most ancient number systems had separate symbols for larger numbers. For example, Roman numerals have special symbols for 1, 5, 10, 50, 100, 500, 1000, etc. and the other numbers are combinations thereof. OK, tell me how to add XLIV and XII… without converting them to our numbers and adding in your head and then converting back. And that’s simple addition, how do you multiply those puppies?
Another example, the Greek and Hebrew numbering systems had separate symbols (letters of the alphabet) for 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300… Again, arithmetic was difficult.
The notion of having only ten symbols, one of them (zero) a place-holder, helped enormously in writing numbers, but more important, in doing arithmetic operations.