The firm showed off a brief trailer for the action title - which it said would be released in 2015 - to coincide with the E3 games expo in Los Angeles.
It also provided more details about how new add-on physical toys called amiibos would interact with games including Super Smash Bros 4.
One industry watcher said Zelda should help improve the firm's fortunes.
"It's a very big one for fans," Christopher Dring, editor of the video games trade magazine MCV, told the BBC.
"If you look at the games sales figures, Zelda is not as big as Super Mario or Mario Kart, but the difference with Zelda is that many fans will buy the console for that game.
"For people on the fence about buying the Wii U - and there are lots of them - it might tip them over. I just wish it was this year, I worry about the firm's line-up for this Christmas."
Nintendo swung to a financial loss last year after its new console - which features a touchscreen controller - missed the firm's own sales forecasts.
It originally projected that it would sell more than nine million Wii U machines over the year to 31 March 2014. In fact it sold just 2.72 million.
"Nintendo's software line-up has to be one of the best in its history to turn the company around," explained Brian Crecente, news editor at the video games news site Polygon.
"Third-party developers like EA, Activision and Ubisoft have retreated from the Wii U because there simply aren't enough consoles on the market to justify the expense.
"Earlier this week, the head of Ubisoft told me that his company has several Wii U titles that are completed but that he won't start selling them until there are more Wii U [consoles] on the market."
Nintendo is promising that the new open-world fantasy-themed Zelda game will mark a "clean break with the past" by letting players travel in the game wherever they want rather than forcing them to follow a set path and complete scenarios in a pre-determined order.
Its lead character Link is also putting in appearances in other titles due for release this year.
He'll first feature in Hyrule Warriors - a battlefield-set title that unites the swordsman with characters from the Dynasty Warriors series - due for release on 26 September.
He will then appear in Super Smash Bros 4 - a fighting game featuring Mario, Sonic and other video game icons - that will launch on the 3DS handheld on 3 October and the Wii U in time for the winter holidays period.
Nintendo revealed that players would be able to create characters in the game in their own image or that of a celebrity, and showed off an avatar of the rapper Ice-T as a somewhat incongruous example.
Previous versions of Super Smash Bros have been hugely popular, and the Japanese firm is throwing its marketing weight behind the title, allowing the public to try out a test-version at the Nokia Theatre in downtown LA over the course of E3.
"A lot is riding on the success of Smash Bros for Wii U and 3DS," said Lewis Ward, a games analyst at the research firm IDC.
"If that game proves to be big hit, it's a system seller, and it could bend the hardware sales curve up appreciably for Nintendo by the end of this year."
Super Smash Bros 4 will also be one of the first games to be compatible with new toys - called amiibos - that contain NFC (near field communication) chips.
These can be used to store data about the player's progress and send the information to and from a Wii U through its controller. The firm said this would allow players to carry their customised settings and achievements to friends' homes.
Activision and Disney have had success with a similar concept for their Skylanders and Infinity franchises
"It's called the toy-to-life genre, and it's getting bigger and bigger," said Mr Dring.
"They are, however, expensive and parents don't always like spending the extra amount. But Nintendo seems to be making it a less essential feature than Disney and Skylanders, where you have to buy characters to unlock content."
Mr Crecente added: "I think amiibo could be a big hit for Nintendo, but it is hard not to wonder why Nintendo didn't do this a year or two ago."
Nintendo said other games to support smiibos would include Mario Kart 8, Yoshi's Woolly World - a forthcoming game based in a world made out of knitted wool - and the platformer Captain Toad: Treasure Tracker.
Other announcements about games due out next year included:
Nintendo has confirmed its first Legend of Zelda video game for the struggling Wii U console.