Zidane could become the first Real coach to lead the Spanish giants to a league title and European Cup in the same season since 1958, after his side saw off Atletico Madrid in their Champions League semi-final on Wednesday.
Madrid went into the match knowing that four points from their final two LaLiga games would guarantee them the crown regardless of Barcelona's efforts and they successfully passed their first test in an expert manner in Galicia.
Ronaldo collected a pass from Isco on the edge of the area before rifling a left-footed shot inside the post to set another personal landmark.
That will played against Celta Vigo tomorrow before the title will be decided in next weekend's final round of fixtures.
Celta's task was made even tougher after 61 minutes when Iago Aspas was sent off for a second bookable offence.
Now, he's breaking a record that's been around for almost half a century. Both calls were debatable and will fuel conspiracy theories always rampant in Spain at this time of the year, although in this observer's view the referee's decisions were understandable.
He said: "Until the final minute we can not think about anything". Toni Kroos completed the scoring in the 88th.
Ronaldo was starting his first La Liga game away from home for almost two months following coach Zinedine Zidane's rotation policy, and he smashed a loose ball high into the net after good work from playmaker Isco. And boy, has that plan worked out perfectly. His shot touch the net. It was deadly finishing of the highest quality. It's the sort of performance he's been putting in consistently over the second half of this season, with 13 goals in his last eight games to put Real Madrid on the brink of an historic double.
At the moment continues to go level with Barcelona, conceding the latter only in the worst difference of goals scored and conceded.
Jimmy Greaves held the record for the most goals in the top five leagues with 366 before Cristiano's strike against Celta.
Individual stats were not the aim Wednesday, though, and Zidane removed his top scorer with the game won and six minutes remaining.
In Serie A, AS Roma provided an unexpected twist to the title race on Sunday with a 3-1 over leader Juventus, which had needed only a draw to wrap up its sixth successive title with two games to spare.