If you need to change your supplier items for any reasons, it can be done in the Supplier settings. Navigate to Settings -> App Settings -> Zip Ordering -> Suppliers. Select the supplier whose item you would like to change, and then click on the Supplier Items tab on the top left. Select the item you'd like to change, and click on the Measurement tab on the left side of the window that pops up. Here you can change any of the following information for that item: case price, case size, pack size, and pack unit. Be sure to click Save in the bottom right corner when you're done.
Hope that helps!