Final Fantasy VII
Zangan never actually appears in Final Fantasy VII, but he performs a crucial act in the events that take place five years prior to the start of the game.
During the incident where Sephiroth destroys Nibelheim in a fit of rage, Zangan - with the assistance of Cloud - helped survivors of the onslaught get to safety. He stayed behind when Cloud and Zack went to confront Sephiroth in order to continue aiding the citizens and only arrived after the damage had been done.
Unable to rescue them all, Zangan decided to save Tifa first. Regretfully he was unable to get back to Cloud and Zack before ShinRa - and Professor Hojo - arrived to clean up.
Martial Arts MasterAfter taking Tifa to Midgar for urgent medical care, Zangan decided to look after Tifa, as she had lost the last member of her family during the incident. He also took this time to start training her to fight as a Monk.
Unfortunately though, Zangan couldn't settle in Midgar and decided to leave Tifa in Midgar. On his travels, he ventured back to the newly constructed Nibelheim and left a note for Tifa.
Final HeavenWhen the party venture to Nibelheim, Tifa finds the note inside the piano that resides in her reconstructed house. It instructs her to continue her training in his absense and it also mentions Zangan's suspicions about what ShinRa has done with the town.
The note also had Tifa's ultimate limit break inside - Final Heaven.
Although what happened to Zangan is unknown, he does mention in the note that he struggles to jump anymore, suggesting that he isn't in the best of health.
Before Crisis: Final Fantasy VII
Zangan appears in Before Crisis, but he has a relatively minor role in proceedings. True to his role as a teacher of Martial Arts, he can be fought in the Before Crisis training mode as a sparring partner.
Crisis Core: Final Fantasy VII
Zangan is only briefly mentioned in Crisis Core and he isn't actually seen at all. His only mention comes via an e-mail sent from Tifa to Zack.