Redirect on checkout if zone_id="0"

Hi!

Due to a ZenCart migration to Opencart 1.5.6.1 I´m having a missconfiguration.

Some of the old clients entry_city field on address_book table lost their city (zone_id) value after migration.
As a result, the zone_id value on oc_address table has the value "0".
I´m figuring that the easiest method to "force" the users to solve the situation is redirect them through controller/checkout/payment_address.php, so, when they are going to make the payment, if check that zone_id='0' > I can do a redirect to /index.php?route=account/address and explain them the situation on a simple warning DIV.

So, I need to avoid the actual:
With something like:
Wich is the error?

Or... how may I check it?

-----------
And also, I may check tables to see if the values match and copy to zone_id the correct value, doing something like that:

SELECT *
FROM `oc_zone`,`oc_address` WHERE `name` = `city`
UPDATE `oc_address`.`zone_id` SET `oc_address`.`zone_id` = `oc_zone`.`zone_id`
LIMIT 1;

Sugestions?

thanks in advance!

Without knowing exactly the type of migration tool you used to integrate these values from Zen-Cart towards OpenCart, I'd say this is where the issue lies due to the way the transactions between the two databases has been processed in the first place. Fixing the integration module would be the first way to go in order for OpenCart to load the geographical settings accordingly without having to make manual adjustments to the checkout steps.

The author colaborate with me importing lot of things more than the default mod has:
http://www.opencart.com/index.php?route ... ion_id=699

For example:

Import more than 4 character words to metatags and tags.
Import 30 first words from descriptio to metadescription.
Importing lowercase, - separated title without spaces to SEO word.
Importing ISBN old field to opencart model/ISBN also.
The shop is perfectly migrated.
Just the old fields mentioned are unmatching.

About the mysql database query... doing:

SELECT *
FROM `oc_zone`,`oc_address`
WHERE `name` = `city`
LIMIT 0 , 30

I obtain:
But now I want to UPDATE `oc_address` SET `oc_address`.`zone_id` = `oc_zone`.`zone_id` when `country_id` is the same.

Ideas?

Solved with payment_address.tpl, at the very top of the file, PASTE:
Thanks.