Dividing by zero ends up in a singularity not 0, 0 is the result of calculating the graph of a function which could at a point end up something like this: f(x) = (2+2x*x+3x)/x in which case there is a situation in which you get a number (2) divided by 0, this in algebra is not possible, in analytical mathematics results in 0 and in higher (college level/ possibly physics only over in the western world, only) math defines a singularity, or (for example) a point in which a 4 dimensional object exists in a 3 dimensional world (this is the case of your standard black hole in essence).