After Carthage's defeat fled to various locations before finally settling down as an adviser to the Seleucid King Antiochus III. When war took place between Rome and the Seleucids, Hannibal offered to take personal command of the Seleucid army, possibly to once again invade Italy. A faction at the court made sure this did not happen. Antiochus took personal command and was defeated.
What if Antiochus had given Hannibal command? He probably wouldn't have entered Greece with as few troops as Antiochus had historically. Rome would certainly have taken the Macedonian wars much more seriously. Hannibal's original army was very Hellenistic in it's composition, with the exception that they did not use the phalanx. Would he have done as well or even better as he did in the second Punic war? Or would his career crash down once again in a second Zama? How would a battle between a Seleucid army led by Hannibal and Rome look like?
What would have happened had he won? Rome didn't very much to be beaten and would have tried again to subdue what is now Macedonia and Greece, the fact that Hannibal defeated them again would have strengthened their resolve even further. I can't see Hannibal somehow turning a Seleucid army again Antiochus by the way.