Zidane was reappointed Real boss in March of this year, but Kroos told Kicker (h/t Marca) of the difficulty he faces in restoring the team to their former glory.
The German said: "It is not easy to take the team back to where Zidane left it. It is difficult to reach that level. Our team was in a different situation when Zidane returned in mid-March of 2019 compared to when he left the team in May 2018."
Kroos' comments featured on Tuesday's Marca front page, via Eleven Sports:
It was under Zidane that Real became the first team to win the UEFA Champions League title three consecutive seasons since the format was changed in 1992. Ajax (1971-73) and Bayern Munich (1974-76) previously lifted the European Cup three times in a row, while Real won the first five tournaments played (1956-60).
Los Blancos completed a league and European double in 2017—their first Liga title in five years—but Cristiano Ronaldo's £100 million departure for Juventus in the summer of 2018 has also had a great impact.
Zidane replaced Santiago Solari midway through last season in a bid to rescue their campaign. Sports writer Alexandra Jonson outlined how things didn't go to plan following his reappointment:
Alexandra Jonson @AlexandraJonson
Zidane had an incredible first term as head coach for Real Madrid winning 3 Champions League trophies and LaLiga once. It only took 9 months (+ 2 managers) from he left until he returned to coach Real Madrid again but the "Zidane effect" have yet to be seen under his second term https://t.co/6lUXzz59Fw
The Frenchman was the third of three managers to lead Real in 2018-19. However, Mario Cortegana of AS reported Solari's record at the helm after he replaced Julen Lopetegui was in fact the best of the bunch:
Kroos, 29, joined from Bayern Munich in 2014 and is part of one area in the squad boasting consistency. He's led the midfield alongside Luka Modric, 33, and Casemiro, 27, for several seasons, but the defence and attack have been more prone to change and fluctuations in form.
"We want to play better football, and more consistently. That's important because, after you do that, the rest comes by itself. If you play better, you'll be in the fight for the titles," he added.
Los Blancos face Red Bull Salzburg in their sixth pre-season friendly on Wednesday. They've lost three of five matches so far and led for the first time in pre-season when they recently defeated Fenerbahce to finish third in the 2019 Audi Cup.
Ex-France defender Frank Leboeuf is a friend of Zidane, and he recently told ESPN FC (h/t Daily Star's Ollie Salt) the relationship between Real's manager and misfit Gareth Bale is like "gangrene" in the dressing room.
That situation in itself is an example of where Real's management and board have room to improve. Real Madrid blogger Lucas Navarrete envisioned the Welshman remaining in Madrid against the odds:
Lucas Navarrete @LucasNavarreteM
Bale’s agent: "There has never been any kind of relationship with Zidane" I expect Bale to stay. He doesn’t want to take a salary cut and Madrid don’t want to let the player go for nothing. As a result, it seems that there’s no market for him. https://t.co/85Z0Nuhwc6 https://t.co/7DqMCq3Tx5
Real have spent heavily to recruit Eden Hazard, Eder Militao, Luka Jovic and Ferland Mendy this summer, but pre-season results suggest chemistry is still lacking.
Los Blancos finished third in La Liga last season but will hope to push Barcelona for the title in 2019-20, with the team scheduled to start their season away to Celta Vigo on Saturday, August 17.