$form->field($billing_address, 'zip',
[
    'selectors' => [
        'input' => '#billing-zip',
        'container' => '#billing-container',
    ],
    'options' => ['id' => 'billing-container'],
])->textInput(['maxlength' => 11,
               'name'=> 'Billing_Address[zip]',
               'id'=>'billing-zip']);

//Shipping
$form->field($shipping_address, 'zip',
[
    'selectors' => [
        'input' => '#shipping-zip',
        'container' => '#shipping-container',
    ],
    'options' => ['id' => 'shipping-container'],
])->textInput(['maxlength' => 11,
               'name'=> 'Shipping_Address[zip]',
               'id'=>'shipping-zip']);