You can track both the ounces and pounds of an ingredient by adjusting which units are being counted. Navigate to Settings -> App Settings -> Zip Inventory -> Ingredients. Select the ingredient you'd like to change, and in the top, select the Reporting Unit you'd like to use. For your situation, select "lb" for pounds. Then, in the bottom right corner, make sure both "Count in Reporting Unit" and "Count in Base Unite" are set to YES. Hit Save (in the top right corner) and you'll be able to track that item in both pounds and ounces.
Hope that helps!