they are functionally the same in terms of what animals are allowed for consumption. the slaughter rules are all functionally the same, except that to be kosher the animal must be slaughtered by someone who has been specially trained and knows the laws, while islam only requires that it is performed by any sane muslim who knows the rules. so, for an orthodox person, one seems to preclude the other. sometimes there are dispensations for islam that says anyone of an abrahamic faith counts. there is also some quibbling about inspecting the animal vs. inspecting its removed organs, and wether or not the name of god is said before the slaughter.

what this probably means is that they paid up with some consultants endorsed by a large enough muslim organization to modify the existing process to achieve a halal cert without losing their kosher cert at the plant.

its super obvious if you ever look up the rules that they came from the same cultural origin, and are only different due to time and space. the people who argue that there is a true difference in the two are pedantic dorks, even in the eyes of hashem/allah.