Unfortunately, like too many companies, Zenith seems to believe that it should hide its history ... it's removed the web page that had instructions for the remote control (formerly at www.zenith.com/how2_program.html). I have been unable to locate any programming information at the Zenith site after 1999.
Click here to email customerservice@zenith.com to complain.
However, the World Wide Web is wonderful...
A search for "allegro remote control" at www.yahoo.com shows a number of sites.
I checked one, and it looks pretty good:
NOTE: I recommend trying several sites. I've noticed that there are minor discrepancies between many of the code lists.