zencart code is a fucking mess... mantaining a patch is pratically impossible..

it's spaghetti code..

if you need more flexibility use magento, the quality is far better..

The Zen shopping cart is another feature-packed, simple-to-use solution backed by a very strong community. As well as offering the same template design structure as osCommerce, Zen Cart offers an excellent range of advanced features that go beyond the general realms of shopping cart functionality. An e-mail and newsletter manager is a very beneficial tool and the flexibility in product and price options is also excellent.

Installation: Setting up is simple. The installer queries the main Zen Cart database and server to discover the specific requirements for your installation. You don't need to be technically savvy or have any knowledge of programming. As long as you know how to install software and use a browser, you can use Zen Cart.

Inventory and Catalog Management: Unlimited categories, sub categories and products are supported and product option boxes can be added in the shape of radio buttons, drop-down menus and more. Flexibility is the key to successful e-commerce and Zen Cart doesn't just recognize this, it openly encourages it. You can offer discounts according to the number of items a customer buys, you can set a minimum or maximum order level and the price can be determined according to the options that your shoppers choose. You can even implement sale prices according to category, region or individual products.

Customer Retention Tools and Features: Customer retention is important. Zen Cart offers a number of beneficial tools to help improve or maximize your retention levels. Gift certificates, order tracking, referral tracking, newsletter management and customer registration options are just some of the features you can implement on your site.

Payment Processing and Gateway Options: Offline and online payment processing can be fully and easily integrated into a Zen Cart e-store. Again, popular online processors like PayPal and 2CheckOut can be offered to your customers. All in all, Zen Cart is a powerful e-commerce tool with a lot of beneficial features and easy installation.

Source: http://www.ecommerce-guide.com/solutions/article.php/3668061