It was a third successive 1-0 win for Los Blancos and saw the LaLiga leaders move a step closer to their first league title since 2016-17, with four rounds remaining.
"It was a match with a lot of fight, intensity and rhythm at a ground where the opponent makes it difficult," Zidane said. "These are three very important points."
Ramos is a guarantee from the spot
Sergio Ramos was roundly ridiculed online by Barcelona fans after he blasted a penalty over the crossbar in the Champions league semi-final shootout defeat to Bayern Munich in 2011-12.
These days, however, the Real Madrid captain is a guarantee from the spot and has now netted his last 20 penalties (22 including shootouts).
The centre-back was on hand to convert the winner again here and said: "I'm the ideal person for that situation. I'm thrilled to do it and if it's to win the three points, even better."
Asked who was better out of Ramos and previous taker Cristiano Ronaldo, Zidane said: "The two are reliable. Sergio is a specialist. He stays after training to practice and it's a plus for us."
Referee talk won't go away
For the second game in a row, Real Madrid took the points thanks to a late penalty and while the decision was not a controversial one, Athletic Club were left frustrated by decisions at San Mames.
Like Getafe on Thursday night, the Basques thought they should have had a spot-kick of their own as Ramos stepped on the boot Raul Garcia in the area, although the attacker was in an offside position, the challenge accidental and the ball nowhere near at the time.
"We are seeing which way these decisions go," Athletic's Iker Muniain said afterwards. "VAR reviewed theirs, but not ours."
There was also an unspotted moment of aggression from the Madrid skipper on Dani Garcia, who was penalised for catching Marcelo for Madrid's spot-kick, albeit after a check from the video assistant referee.
Zidane, though, said he was 'tired' of critics saying that Madrid only win because of referees. "People should respect Madrid and the players, who are the ones out on the pitch," he said.
More defensive excellence as Militao shines
The absence of Raphael Varane with a neck problem caused some anxiety among madridistas ahead of this match, but Eder Militao came in and played perhaps his best game yet since signing from Porto last summer.
The Brazilian was excellent alongside Sergio Ramos at the back and another clean sheet allowed Los Blancos to secure a narrow victory in Bilbao.
"He played a good game," Zidane said. "We are showing our strength. Our balance. When we lose the ball, we all defend."
In goal, Thibaut Courtois was also oustanding again and Madrid have conceded just 21 goals in 34 games in LaLiga this season.
LaLiga is within reach after tough week
This week's games against Getafe and Athletic always looked likely to be key to Madrid's title hopes and Los Blancos have come through both with maximum points. LaLiga is now within reach.
After those two hard-fought wins, Zidane's side now appear to be in an unassailable position, whatever Barcelona do in their remaining fixtures.
"We are focused on what we are doing," the Frenchman said. "We just have to think about the games we have left."
Alaves at home is next, followed by Granada away, then Villarreal at the Alfredo Di Stefano and a trip to Leganes on the final day. With the toughest tests overcome, it should be a formality from here.