Search customer issue

We have a customer ID zz2535EDAL. If we search by starting with zz, the Customer ID zz2535EDAL is shown on the list; but if searched by starting with one more character, say, with zz2 or zz25; the customer ID zz2535EDAL is not shown on the list. Anyone know why this happens? Please help. Thanks.

Regular search or custom quick search?

search by clicking on “Customer…” in Customer Maintenance (Customer Search).