After pressing all kinds of button combos, I helld the learn button for about ten seconds and it lit up. I found the smart 15 manual on this site and punched in codes for many VCRS and the 3 TVS I have. I got the Zenith to work.
Basically hold the learn button about 4- 10 seconds the teach and learn buttons will flash , press the correct power button you want to program, look up the code on the smart 15 manual, input the 3 digit code and enter (ENT). it should stop flashing for a second and the learn light will hold then it flashs again. Hold learn for a couple seconds longer the lights go out and try the code. Repeat with another code if not working. Repeat for other functions. I have the same remote as the original poster