And Los Blancos followed up that triumph with a victory in a goal-laden match at Benito Villamarin that swung back and forth between two teams who dazzled with a stunning display of attacking football.
Madrid took an early lead through Asensio but Betis, thanks largely to the evergreen, effervescent Joaquin, scored twice in four minutes to turn the match around before half-time through Aissa Mandi and a Nacho own-goal, strikes which followed Marcelo limping off with a hamstring injury for the visitors.
LaLiga's champions recovered brilliantly after the break, though, with Sergio Ramos heading in the equaliser, before Asensio struck a fine finish to put his side back in front - recording Madrid's 6,000th LaLiga goal in the process.
Cristiano Ronaldo, who scored twice against PSG to continue his blistering 2018 goalscoring form, seemingly wrapped up the points with Madrid's fourth goal after 65 minutes.
Zidane's men survived a late fightback from Betis after Sergio Leon struck, though, with Karim Benzema coming off the bench to score Madrid's fifth, and his side have a six-point cushion in the last of LaLiga's four Champions League qualification places, with league games against Leganes and Deportivo La Coruna to come for Los Blancos in the next six days.
Madrid were without Toni Kroos due to injury and Zidane rested Luka Modric, Benzema and Isco, but despite the changes the visitors took the lead after just 10 minutes.
Former Madrid keeper Antonio Adan could only parry a powerful shot from Ronaldo back into the danger zone, with Asensio perfectly placed to guide a header home for his fifth league goal of the season.
Betis responded well, Keylor Navas making a sensational one-handed save high to his right to keep out Joaquin's whipped free-kick, but Betis soon earned just reward for their exerted pressure.
Mandi had already headed one Joaquin corner wide but he was on target after 33 minutes, overpowering Casemiro in an aerial challenge to nod past Navas.
Ronaldo then had a goal rightly ruled out for offside and Betis went straight down the other end to take the lead.
Joaquin was again instrumental, driving at the Madrid defence and slipping in Junior Firpo, whose shot squirmed through Navas and bounced in off the unfortunate Nacho.
Within five minutes of the restart Madrid were back on level terms, though, Ramos powering home a right-wing Lucas Vazquez corner with an unstoppable thumping header.
And the goals continued to flow, Asensio on target with his second of the game to restore the Madrid lead, cushioning home a lovely first-time finish from Dani Carvajal's cutback after a brilliant run down the wing from the right-back.
The Madrid comeback was apparently completed after 65 minutes, Casemiro finding Ronaldo and the Portugal superstar smashing in his 10th goal in his last six appearances.
8 - Cristiano Ronaldo has scored eight goals in La Liga since the start of 2018, more than any other player. Lethal. pic.twitter.com/XgcUuma2cB— OptaJose (@OptaJose) February 18, 2018
There was more drama to come as Madrid grew complacent, though, with Betis battling back again when Junior whipped a brilliant low ball in behind the defence for Leon to tap in at the back post.
But despite throwing everything at Madrid, Betis could not find the equaliser and substitute Benzema completed the scoring in the second minute of stoppage time, polishing off a slick one-two with Vazquez to score his first LaLiga goal since November.
FT: @RealBetis_en 3-5 #RealMadrid— Real Madrid C.F. (@realmadriden) February 18, 2018
(Mandi 33', Nacho (og) 37', Sergio León 85'; @marcoasensio10 11', 59', @SergioRamos 50', @Cristiano 65', @Benzema 90'+2).#Emirates | #RMLiga pic.twitter.com/517KvpEJPK