This plugin allows you to list products directly under your subcategories.
By default, Zen Cart does NOT allow products and subcategories to exist on the same level. This plugin retains that restriction, but allows you to display products after listing your subcategories. It does not move/copy/link your products - it leaves the category structure intact.
This plugin will just display all of the products from all matching subcategories right under the subcategories list. This allows the visitor to either browse all of your products in the top level category, or to narrow down the list by using subcategories.
NOTE: some CSS tweaks might be required after installing the module - please understand that every store is unique it's almost impossible to create this kind of module that will work out of the box without any tweaks for any website using any template.