Have you migrated your ZenCart store yet? If not, you can try this tool. I used it and it worked well.
I would love to help you with Zen Cart to Magento migration. Here’s a migration tool from Cart2Cart you may find useful: https://www.magentocommerce.com/magento-connect/cart2cart-zen-cart-to-magento-migration.html
Swiftly and securely, it will move your database from your old Zen Cart store to a new Magento 1.9.2 one in terms of several hours depending on store’s size. The service is fairly easy to use and requires no coding at all (or software installation). All you have to do is to establish the connection between the stores and choose the entities you’d like to move. You may find detailed info on its official website if interested.
By the way, Cart2Cart also supports migration to Magento 2! I guess there’s more sense to move to the latest Magento version, isn’t it? Anyways, if up to you to decide.
Hope it’ll help!
There are a lot of migration tools, truly Cart2Cart one of the most famous, but the only I used... So my opinion isn't critical and can be the only to be taken into account...
However there are a lot of tools, the most of them don't allow you to transfer all data you have. And they won't let you do that in the nearest future at least. Just because it is very complicated...
Here is the article which may be usefull to you - http://provectus.com/blog/magento-re-platforming-checklist
As I know, demand of exporting data from zencart to magento is quite large in first six months of 2016. Your problem is shown in some topics. I see zen cart to magento migration extension of Lit-Extension can be a smart decision for your online business to migrate from zen cart to magento.