Monoid with zero element

Mzero.hs

module Mzero where

import Data.Monoid

class Monoid a => MonoidZ a where
    zero :: a

    mconcat :: (Eq a) => [a] -> a
    mconcat = go
      where
        go [] = mempty
        go (x:xs) | x == zero = zero
                  | otherwise = x `mappend` go xs

instance Num a => MonoidZ (Product a) where
    zero = 0
    
instance MonoidZ All where
    zero = All False

instance MonoidZ Any where
    zero = Any True