I think because of the presence of Simone Inzaghi as the new manager, Al Hilal was surprisingly able to beat Manchester City and advance to the quarter finals.
Al Hilal chances of advancing to the semifinals are very open, expectations for the Saudi Pro League representatives are higher after defeating Pep Guardiola squad, although Fluminensi cannot be underestimated.
Overall, I predict that Al Hilal journey may only reach the semifinals, because on that path there is Chelsea, which can be a big obstacle to reaching the final.
If Al Hilal can do the same like playing against Manchester City, Fluminense won't be a threat for them advancing into semi finals. Chelsea at this level isn't the best opponent that can stop Al Hilal from advancing further, with their struggling performance the gap performance seems to be wide, Al Hilal started with Real Madrid, did the same to Manchester City while Chelsea were struggling against Benfica if not for the red card that helped them.
Chelsea has to beat Palmeiras tomorrow to decide their next opponent while Al Hilal vs Fluminense will be playing today.