Soler's treble – the first from a Valencia player in the top flight since September 2017 – was added to by an own goal from Raphael Varane, who deflected Maxi Gomez's cross beyond Thibaut Courtois. Madrid's goalkeeper had initially saved Valencia's first penalty, which was retaken due to an infringement from Yunus Musah.
Madrid started brightly and led through Karim Benzema's brilliant opener but conceded four goals in a league match for the first time since a 5-1 defeat to Barcelona in October 2018 – the result which cost Julen Lopetegui his job.
Zidane, who Lopetegui replaced, accepted the blame for this Madrid display, acknowledging they must solve their defensive problems having conceded 14 goals in seven games in all competitions since returning from October's international break.
"Three penalties, an own goal, it's too much," said Zidane, whose side are fourth, four points behind leaders Real Sociedad.
"The fault is mine because I am the coach and I have to find the solution. I can't justify what happened. It's a bad day, there are no excuses. We must improve defensively.
"I don't think Valencia have been tactically better than us. The only thing is that we started well and everything changed after the goal.
"This is difficult to understand. But yes, the maximum responsibility is mine. We must find solutions after the goal they scored."
While Madrid's defence endured a collective nightmare, with Varane scoring his second own goal in the space of five appearances in all competitions, playmaker Isco was equally disappointing at the other end.
Starting for the first time in LaLiga since October 17 – when Madrid lost 1-0 to Cadiz – the 28-year-old had just one shot and created only a single chance before he was taken off in the 83rd minute. Isco has played a meagre two key passes all season.
Zidane defended the player, however, saying: "Isco has tried, he has done well like everyone else. In the end, everyone loses, there is not just one guilty party."
Madrid were without holding midfielder Casemiro who, like Eden Hazard, is isolating after testing positive for coronavirus.
The champions have won just one of the six LaLiga fixtures in which Casemiro has not started since the start of last season, but Zidane insisted the Brazilian's absence was no excuse.
"We can look for a thousand things – you don't have to look for excuses," he said. "They are all Madrid players."