form-checkout.php

<?php
/**
 * Checkout Form
 *
 * This template can be overridden by copying it to yourtheme/woocommerce/checkout/form-checkout.php.
 *
 * HOWEVER, on occasion WooCommerce will need to update template files and you
 * (the theme developer) will need to copy the new files to your theme to
 * maintain compatibility. We try to do this as little as possible, but it does
 * happen. When this occurs the version of the template file will be bumped and
 * the readme will list any important changes.
 *
 * @see 	    https://docs.woocommerce.com/document/template-structure/
 * @author 		WooThemes
 * @package 	WooCommerce/Templates
 * @version     2.3.0
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

wc_print_notices();

do_action( 'woocommerce_before_checkout_form', $checkout );

// If checkout registration is disabled and not logged in, the user cannot checkout
if ( ! $checkout->is_registration_enabled() && $checkout->is_registration_required() && ! is_user_logged_in() ) {
	echo apply_filters( 'woocommerce_checkout_must_be_logged_in_message', __( 'You must be logged in to checkout.', 'woocommerce' ) );
	return;
}

?>

<form name="checkout" method="post" class="checkout woocommerce-checkout" action="<?php echo esc_url( wc_get_checkout_url() ); ?>" enctype="multipart/form-data">

	<?php if ( $checkout->get_checkout_fields() ) : ?>

		<?php do_action( 'woocommerce_checkout_before_customer_details' ); ?>
		<div id="digthis-step-1" class="steps">
			<div class="col2-set" id="customer_details">
				<div class="col-1">
					<?php do_action( 'woocommerce_checkout_billing' ); ?>
				</div>

				<div class="col-2">
					<?php do_action( 'woocommerce_checkout_shipping' ); ?>
				</div>
			</div>
			<div class="form-row">
					<input type="hidden" name="current_step" id="current_step" value="step-1">
					<input type="submit" name="verify-checkout" id="verify-checkout" value="Verify Checkout">
			</div>
			<?php do_action( 'woocommerce_checkout_after_customer_details' ); ?>
		</div>
	<?php endif; ?>
	<div id="digthis-step-2" class="steps">
		<h3 id="order_review_heading"><?php _e( 'Your order', 'woocommerce' ); ?></h3>

		<?php do_action( 'woocommerce_checkout_before_order_review' ); ?>

		<div id="order_review" class="woocommerce-checkout-review-order">
			<?php do_action( 'woocommerce_checkout_order_review' ); ?>
		</div>

	<?php do_action( 'woocommerce_checkout_after_order_review' ); ?>
	</div>
</form>
<!-- move to own css file -->
<style type="text/css">
#digthis-step-2{
	display: none;
}	
</style>
<script type="text/javascript">
//should be move to its own js file
	jQuery(function($){
			$( document.body ).on('checkout_error', function(){

				var digthisError = $(document).find('#digthis-prevent-error');
				if( digthisError.length != 0 ){
						$( '.woocommerce-NoticeGroup-checkout, .woocommerce-error, .woocommerce-message' ).remove();
						$('.steps').hide();
						/*Change it so validation stops*/
						$('#current_step').val('step-2');
						$('#digthis-step-2').show();
				}

			});
	});
</script>

<?php do_action( 'woocommerce_after_checkout_form', $checkout ); ?>

functions.php

<?php
add_action('woocommerce_after_checkout_validation', 'digthis_two_step_checkout_validate', 9999, 2);
function digthis_two_step_checkout_validate($data, $errors) {
	
	$step = filter_input(INPUT_POST, 'current_step');
	
	if( empty( $errors->errors ) && $step == 'step-1'  ){
		$errors->add( 'digthis', __( '<span id="digthis-prevent-error">Digthis Error</span>', 'woocommerce' ) );
	}

}