Interoperability Fixes have been posted for Edit Orders 4.x and some of my Zen Cart mods:
Zen Cart Product Bought is a template mod that allows you to display messages if a particular product has been purchased (ever, or within a set period of time). Here’s a video that shows it working:
Zen Cart Product Bought allows you to check to see if a logged in customer has purchased a specific product in the past. It’s perfect for cross selling and upselling messages on the product info page or in the shopping cart. You can even check to see if a product has been bought within a particular time period, such as in the last 90 days.