As I always do, I agree with SS.
Zelda is BOTH an Action/Adventure and a Role Playing game. A role playing game is simply a game where you take on the role as one set character whom you raise up to get stronger and fight harder enemies. The way I described it might be more "Pokemon" than Zelda, but indeed in Zelda, you get more weapon upgrades and instead of levels, you gain "Heart Containers". An action/adventure game would be much like the corny batman games that come out for game boy, but in real definition, it is a game where you accomplish required tasks to go on to a higher "level", instead of going out on your own and working on side quests like in Pokemon. But the ingenious creators of the Zelda series decided to combine the two.
This will speak for Majora's Mask game, since it is the most recent. I own other Zelda games, but I will only use this one because I was just playing it yesterday.
Zelda has:
ยค A complete, packed timeline filled with several paths you can take. Examples of this are:
--There are only 3 Days in Majora's Mask to accomplish a whole bunch of tasks required. In order to complete this game, you must relive these three days again and again, starting time over before the world ends at 6 AM on the end of the final day.
--Many side quests found in Majora's Mask are indeed where you must take on the role of "matchmaker" in the cases of:
----Uniting Kafei and Anju for their wedding
----Finding Madame Aroma's son
----Finding the photographer's prodigal son
----Rescuing the witch Koume
----Helping the postman reach his highest priority
--Simply put, Majora's Mask is a game where you fulfill everyone's final wishes before the world ends and they die.
--Majora's Mask does not contain turn-based fighting, it relies on your strategy of attack and dodge to defeat an enemy. That is a characteristic of an action game. Heck, Super Mario is an RPG, but it's fighting is based on attack-and-dodge too.
--In Majora's Mask, every one of the four Temples you must destroy an enemy in has a very complex history to it, and the enemies are powerful and difficult to defeat, so you must acquire hidden items within the temples to destroy the enemy. Adventuring into the unknown is the adventure portion of the game. After completing the adventure, you fight a final "boss" which is the action part. After defeating the boss and destroying the evil that has ruined the land, you must do several side quests in order to call the level "complete". In the case of convincing Deku King to not punish an innocent monkey for murdering his daughter by rescuing her from the temple, this is the RPG part of the level. In order to do one major task in the game, you must combine action, adventure, and RPG.
--Zelda has collecting items in it too. Especially in Majora's Mask, where collecting 20 masks by making 20 different people have their final wishes granted. Collecting and trading items is part of RPG too.
I could go on forever... @_@ But I'll stop now.
In conclusion, Zelda is both an action, adventure, and a role playing game. Like it or not.