Better Together allows you to pair items for discounting.
You may specify
But in the free version, adding Better Together discounts requires editing a file and modifying PHP code.
The Zen Cart Better Together Admin Panel gives you a user interface to add every type of linkage that Better Together supports.
Better Together discounts pairs of products. You can create discounts that link two products, two categories or a product and a category. If you really want groups of three or more products in a discount (buy 2, get one free), please look at Zen Cart Discount Chooser.
For more information, please visit this product's webpage.