Zero is even because:
1) It's evenly divisible by 2 leaving no remainder (0/2 = 0 r 0)
2) Like all even numbers it ends with 0, 2, 4, 6 or 8
3) The integers alternate odd, even, odd, even... Zero is between two odd numbers.
4) The sum of two even numbers is still even. Since 0 + (even) = (even), 0 must also be even.
Those that are saying zero is neither are confusing this with negative and positive. Zero is a neutral number (neither negative nor positive). But this doesn't affect its ability to be classified as even.
Zero is definitely *even*