The two young royals, though friends, are as different as their engagement pictures: Prince William and Middleton, both 28, released retouched photos taken by master lensman Mario Testino, while Phillips, 29, and Tindall, 32, chose casual outdoor shots of them wearing jeans.
William is world famous, a heartthrob, formerly the most eligible man in England if not the world. Phillips has carefully cultivated a "Zara Who?" persona, which seemed to spring naturally from her mother, Princess Anne, who decided early on that her two children would not use any royal titles.
The lack of royal formality has not hindered Phillips, who has become a master equestrian in her own right, winning several titles and earning a BBC sports personality of the year award for her horsemanship.
She has not announced the time and place of her wedding - etiquette suggests she will not schedule it close to William's big day on April 29 - and her wedding is likely to be a much smaller, more informal event.
"Zara Phillips doesn't use the royal title, and that was reflected in the low-key way they announced their engagement, with no special photograph, no special hairdo, very laid back, so already the tone of their wedding is very different than Kate and William's," said Deborah Joseph, editor of Brides magazine. "They will have more freedom to do what they want, they won't have to adhere to protocol."
She said Phillips will not have to be as cautious as Middleton in her wedding choices because Middleton is marrying into the royal family and will have to make a good impression.
"Kate can't put a foot out of place, but Zara doesn't need to worry as much, she's grown up with it, the queen's her grandma," said Joseph. "Zara's very quirky, and quite rebellious - remember she once had her tongue pierced. Kate's the opposite, much more classic and safe."
The queen has eight grandchildren. The oldest, Peter Phillips, 33, married Canadian Autumn Kelly in 2008. His younger sister Zara is now engaged, as is Prince William. Red-haired Prince Harry, 26, is single, as are Prince Andrew's two daughters, Princess Beatrice, 22, and Princess Eugenie, 20. Prince Edward has two young children: Lady Louise, 7, and Severn, 3.
Having two members of the same family get married during a short period of time can sometimes lead to tensions and rivalry. And it's not easy to compete when your cousin's wedding ceremony is expected to be televised live around the world.
Wedding planner Mark Niemierko said he advises clients in similar situations to let several months or more elapse.
"You don't want it anywhere close to the other person's date," he said. "In Zara's case, I would go to autumn - wait the whole summer, it's kind of nice to let the dust settle, so you and your friends can be excited about it. You want to have some time."
He also would urge her to choose a country wedding in contrast to William's gathering at London's Westminster Abbey.
"If your cousin is doing it in London, maybe do it outside of London," he said. "You don't want to be drawing comparisons, you want to avoid that at all cost. Zara doesn't have to conform."
But in one case - the dress - Niemierko says Phillips should not try to anticipate what kind of gown Middleton will wear.
"The less you know about the other person's dress, the better," he said. "If Zara finds the designer who is her style, she should pick it."
