Prior / Pryor to roughly the 1850's (on the Greco-Roman calendar) religious jews and religious muslims dwelled together in relative peace and harmony. Some "religionist" (whom promote there own world for the sake of, some say, an archaic form of power, money and control, say because 'they', during those times, were more religious or observant.
Others take a more rationalistic or enlightment point of view, in that, language and early modern technology began to reach the beginning stages and, along with that, various religious institutions were worried, even during that time period, of 'what would happen next'. Later on, some religious movements played on peoples 'human and animalistic' emotions to promote or destroy various causes and movements.
Another perspective suggests that the reason for dissention, over time, and even the reason for military conflicts and wars was simply economic and/or educational class rivalry. The proverbial rhesus lining on sides of the fence to throw popes / poop, etc. Some would say the reason(s) for the invention and deployment of the Roman's shield...
In other words, there are no 'Kosher and Halal restaurants'. The very concept is at odds. It's either a kosher restaurant or it is a halal restaurant. From the 'old testament / Torah' - 'the older shall serve the younger'. Jews, because of the Oral Tradition and Masoretic Text, say that the Torah / Old testament is talking about the 'spiritual age' of the soul that is currently dwelling in the person. Christians and Muslims say the concept and book(s) are in the 'literal' number of years of the humans/animals lifespan on Planet Earth.
I'm sure some religious scholars could, however, for the sake Reese's pieces, perhaps with some level of remorse or regret, authorize various establishments. However, both proverbial 'camps' would find the idea, "outrageous, egregious and preposterous ."
An authorized non-kosher item, a.ka., halal within the context of a glatt kosher or kosher authorized restaurant is, in some scholars opinions, actually, potentially, dangerous. The same for for halal.
In other words, at times, these concepts, ideas and studies ares, "too lofty" for my current knowledge sets and studies.