Zen Cart Bogo Discount
The BOGO Discount extension permits you to offer discounts that are structured as:
Buy One Product Get another Product Free
Most of the times there is requirement for One purchase of "X" Product Give "Y" product free. We have developed such Bogo Module in Zen Cart
1) Get Shaker Free with Protein Powder (As mentioned in attach image).
2) Get Tie Free with Shirt.
We have developed such module so as client can enter product id on edit product info page whichever he wants to give free with that product.