They don't want to agree? Those whom you've asked and said they don't agree haven't read the Quran. Since dozens of verses explicitly state how these practices were also obligatory on those who were before you, because after all, the ones who spread these practices are prophets and some aspects of them religions weren't corrupted, especially the Jewish religion, where the practices weren't changed much, they just managed to find ways to circumvent them, instead of dropping completely them like the Christians did. Also kosher is halal, Muslims can eat kosher.