Ronaldo's double in Saturday's final at Cardiff's Principality Stadium, allied to goals by Casemiro and Marco Asensio, earned him a fourth Champions League win and gave Madrid their third in four years and 12th in total.
Ronaldo, 32, has now scored 600 career goals for club and country, including 105 in the Champions League, and has finished as the top scorer in the competition for the last five seasons.
"I think people don't have words to criticise, because the numbers don't lie," he told reporters after receiving the man-of-the-match award from his former Manchester United mentor Alex Ferguson.
"This year was amazing again, last year was amazing too. Now I have two or three days off to rest and after we have a (World Cup) qualifying game for Portugal and we have the Confederations Cup.
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"It's a long season, but I'm motivated, I'm happy. I'm in a good moment. My age is just a number. I feel like a young boy."
Madrid became the first team to defend the European Cup successfully since Arrigo Sacchi's AC Milan in 1990 and the first to achieve the feat since the competition relaunched as the Champions League in 1992.
"Having said that, you know how things are. Next year it's going to be even more difficult. We're going to have to work very hard to win once again.
"But today we can say that we are a very good team and that we deserved to win the league and the Champions League. It was not easy."
Zidane, 44, led Madrid to glory in last season's Champions League less than five months after succeeding Rafael Benitez to take up his first managerial role.
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The former France playmaker's contract expires in a year, but he said he was not thinking about leaving.
"I'm not going to confirm I'll stay here all my life. That's impossible to say," he said.
"But I'm extremely happy and I'm very grateful to the club for giving me the opportunity to coach these fantastic players.
"I have a one-year contract left. I think I'll be here next year!"
The emphatic nature of Madrid's victory removed some of the gloss from Mario Mandzukic's sensational equaliser for Juve, which cancelled out Ronaldo's 20th-minute opener.
Casemiro restored Madrid's lead just after the hour and further goals from Ronaldo and substitute Asensio confirmed victory before Juve substitute Juan Cuadrado was harshly shown a second yellow card for pushing Sergio Ramos.
Juve have now lost five successive European Cup finals and a record seven in total.
The Turin giants, Serie A and Coppa Italia winners this season, fielded a starting XI with an average age of 30 years and 336 days, but coach Massimiliano Allegri dismissed talk of decay.
"(Gianluigi) Buffon will still be the goalkeeper next year. The same applies to Andrea Barzagli, who will still be with us for at last another year. They've still got lots to give.
"If our current team is complemented with new players, we'll be really competitive in the Champions League next year.