But if in the end he succeeds in getting them to put their egos aside and switch to a collective game then I think Madrid will really be very well protected in terms of goal productivity because indeed these two players are very solid individually but quite bad when placed together in one club so far.
This reminds me of the time when Zidane coached Real Madrid and they won the UCL three times in a row. Many said Zidane wasn't a genius coach, but he was lucky to coach Real Madrid alongside the prime Ronaldo. His passing tactics to Ronaldo became a topic of conversation on social media at the time. But what's not known is that teams with star players usually have big egos. Everyone wants to be the main character, and that's what can make a team with many star players fail. But Zidane was able to overcome each player's ego so they could play collectively. Real Madrid currently also has many star players, especially in the attack. Mbappé and Vini are two of the best strikers in the world today. They have big egos to score goals, become top scorers, and win individual trophies because they have the ability to do so. This will be Xabi's first job: to make Real Madrid play more collectively as a team, rather than individually.
You are very correct, clubs with star studded team most times suffer this situation of ego amongst their players and when this has eaten deep into a team it becomes difficult for them to play as one and it kills team work. Not many managers are able to manage such team effectively. I think Zidane did a great job managing the team he had with Real Madrid. Xabi will have to find a way around this problem before it ruins his spell.