Ronaldo's now the first player ever to score in three Champions League finals - 2008, 2014, 2017.
The Italians let in more goals on Saturday than the three they had conceded in the 12 games they played to reach the final as a much-vaunted Real attack versus Juve defence scenario went emphatically in Madrid's favour.
But within seven minutes, Ronaldo was shaking his head with a scowl after seeing an equalizer of individual brilliance.
Zidane's joy was his former club Juve's despair, Massimiliano Allegri's side crashing to a fifth successive defeat in Champions League finals and seventh in total, extending their own desperately unwanted record.
In winning his second Champions League as a manager, Zinedine Zidane has fashioned and honed a team that so fantastically responded to every challenge, that just went up a several levels according to the severity of the test.
His first effort was his club's 500th in the competition.
Those misses would prove costly as Cristiano Ronaldo, the epitome of precision, played a one-two with Dani Carvajal, before stroking a finish home, albeit with a slight deflection off Leonardo Bonucci. The Frenchman prefers a 4-3-3 when all players are available to him, and Real Madrid are likely to feature in that very formation, with Juventus likely to do the same.
The Spanish giants who come into the game as La Liga champions, will face Juventus in Cardiff in what promises to be a tight encounter.
It owed much to Madrid controlling midfield, largely thanks to Modric, who set up Ronaldo's second. Cristiano Ronaldo scored a brace in the match, while Casemiro and Marco Asensio also scored to seal Real Madrid's victory.
Madrid's supremacy was clear in the second half.
Modric sped to the byline on the right and crossed, and Ronaldo darted ahead of Bonucci at the near post to guide a shot past Buffon. Karim Benzema is one further back on five.
There was still time for a fourth for Madrid, with substitute Asensio finding the bottom corner after being found in the middle by Marcelo in stoppage time.