Kya hai Marbury vs Madison aur Kesavananda Bharati ka Fark?

Hey bhaiyya, I'm lost between these two SC decisions. Marbury vs Madison says that if a law is unconstitutional, it gets struck down, while Kesavananda Bharati case changed our Constitution's amending clause, saying our Parliament can amend even part of a fundamental right. But isn't that a huge loophole? Someone explain the difference between these two, please. How do they impact our constitutional laws? Kya unka effect hua hai?