Question

why is zero called neutral

Answer 1

because it is neither even nor odd

Answer 2

Zero (0) is generally considered neutral because when we consider a number line, we take 0 as the middle point, having infinity on either side.
   
                                                         OR

Zero is also considered neutral because it is an Additive Identity, i.e, when a number is added to 0, it always remains the same number (not having any change).

Kindly Find Whichever Suits You : )
Happy To Help