The Spain international put Madrid two goals up against Inter in their eventual 3-2 win over the Italian side in Tuesday's entertaining Champions League clash.
Ramos' landmark header came on the same day he had been linked with a move to Juventus but Zidane is adamant his captain is going nowhere.
"I have no doubt that he will stay," Zidane said at his post-match news conference. "He is our leader and of course we love him forever."
Of his 100 goals, 55 have come via his head and the skipper admits he took pride in scoring from a set-piece against Inter.
"We knew from what [Samir] Handanovic said that they had been studying our corner deliveries with Toni [Kroos] finding me," he told Movistar after the game.
"But the more we can continue to surprise our rivals, the better. They know what they are doing, they have a very defined philosophy and they made the most of that.
"It's a good result, and three points in a group that had started to look complicated for us."
Asked about his achievement of reaching three figures for goals in Madrid colors, Ramos said: "It's not bad, and it is nice that it is recognized.
"It's not a figure which defenders usually get to. Hopefully, there'll be many more."
Ramos' header came eight minutes after Karim Benzema had profited from an Achraf Hakimi error to open the scoring for Madrid at the Estadio Alfredo Di Stefano.
Inter recovered through goals from Lautaro Martinez and Ivan Perisic but Rodrygo regained Madrid's lead in the 80th minute after being set up by fellow substitute Vinicius Junior.
Madrid had more of the possession (55 percent) and managed seven shots on target to Inter's three, and Zidane believes the right team won in the end.
"There was always going to be tension because we were playing a strong rival," he said. "We have suffered but we must congratulate the players because they deserved it.
"We started very well, pressing up as we wanted. We made it 2-0 but then had difficulty keeping up with the ball. Then the second half was very close, but that is normal.
"The team has an impressive character and they want to show that they can do. We are going to have difficulties in all the games because I watch a lot of games and I don't see any of them win the games easily."
Madrid have conceded two or more goals in five consecutive Champions League games for just the second time, having previously done so in 2001, and Zidane admits it is now about finding the right balance between attack and defence.
"It is true – there is always a balance to have," he said. "We played a side who are also good on the counter, but how long ago was it that they said we do not score such goals?
"We have to keep working because it is not easy to do the two things together."
Madrid are third in Group B, behind Borussia Monchengladbach and Shakhtar Donetsk, after moving onto four points from three games.