Disable Postcode/ZIP Validation @ WooCommerce Checkout

To make ZIP code not required @ WooCommerce Checkout page put this code into your theme’s functions.php file.

add_filter( 'woocommerce_default_address_fields' , 'override_postcode_validation' );

function override_postcode_validation( $address_fields ) {
  $address_fields['postcode']['required'] = false;
  return $address_fields;
}

More info @

https://docs.woocommerce.com/document/tutorial-customising-checkout-fields-using-actions-and-filters/

and

https://gist.github.com/ddbs/9282829