AZA 
x AZZA

AZZZZZA 
Substitute a single digit for Z. Substitute any digit for each A. The number for Z must be different from the numbers for A. There are no leading zeros. What are the possible solutions?
Source: Reader Jimmy Chng Gim Hong, though I believe I've seen it elsewhere.
There are only two solutions:
723 * 7223 = 5222229
645 * 8441 = 5444445