We worked on system all week - Isco after Madrid derby triumph
Real Madrid midfielder Isco praised Zinedine Zidane's tactics after the LaLiga leaders accounted for Atletico Madrid.
Cristiano Ronaldo scored a hat-trick as Madrid claimed bragging rights over Atletico in Saturday's derby.
Madrid lined up in a 4-4-2 formation with Isco playing just behind Ronaldo at the Vicente Calderon, and Atletico struggled to cope.
"During the week we were working on this system and it worked out well in the end," said Isco.
"The team struggled in certain moments but we came out on top. We played perfectly, understanding each moment in the game and we are happy with the three points."
"I am happy with my work and the team's work. Winning 0-3 here is difficult and it is something to be proud of," the Spain international added.
"We went into the game really fired up, we had a lot of the ball and we got the first chances. After the goal perhaps we eased off a bit but we knew how grind Atletico down and we got an overwhelming result."
Madrid are now four points clear of second-placed Barca and nine ahead of Atletico after 12 matches.
But Isco insisted: "There is still a lot of time in the league and in previous years we went ahead and failed to maintain regularity. We took three points, but we must continue."