Also not the same. You can't say "the number of apples is no", but you can with "zero".
Put another way, the invention was not literally the word "zero", or anything to do with language per se. It was the idea that you can think about lack of existence in the same was that you think about counting, i.e. treating the idea of there being two apples and the idea of there being zero apples as two examples of the same thing in your mind, instead of treating one as being in some way fundamentally different.
Being raised with a maths education from a young age now, it's easy to see this as obvious, but there was a time in human history when it wasn't.
Also, I wasn't disagreeing with the Cartesian coordinate system being more significant.
The fact is, zero's usefulness is a bookkeeping device. "There are zero apples" is not better or more useful than "there are no apples." That's not why zero survives. You can wax poetic day and night about what a mind shift "lack of existence is." You're not getting it. You're missing the point. What does that _enable_ that "no apples" does not? That's the measure of its usefulness, right?
It enables positional notation. That's zero's primary gift to the world. It is a necessary bookkeeping device for positional notation. And the measure of positional's usefulness over its predecessor, additive numerals a la the Roman system, is so profoundly great that no argument need be made. No waxing poetic is needed. No "it seems obvious now but back then." It's just indisputable.