When we sell our greeting cards wholesale, the only relevant ID we absolutely need is our internal model number. So we enter that in the, you guessed it, model number field. All lists of products can be sorted by model number in either admin or the store front. For us, and for our customers, the internally generated zen id number of each product is never looked at , and for that matter it is not visible to the customer at all (unless they can read the URL in the address bar.) So?
So... if you're not already using the model number field, use that for your own id number. If you are already using the model number field, I've seen discussions here on the forum about adding fields to product info for various uses, either in just the admin, or in the store front too.
In short, ignore the zen id number.
Rob
Breakfast: the most important donut of the day.