One major thing seperating christianity and islam is death of jesus and trinity.
Islam does not beleive in trinity or that jesus is son of god no do they believe jesus died.
They beleive jesus "look like" died instead.
They do beleive in old testament and also holy Quran.
I beleive one can beleive in both.
One hand bible another Holy Quran in some way shape form....
Then theres people beleive other theories and bible coding and much other things.
some people have said jesus and mohammed were homosexual in times interacting and history books got it wrong regarding the time.
that they hid men in burkas to cover up homosexuality they were to afraid to stand for or they kept straight woman in burka nd used them as slaves.
Muslims beleive isa jesus existed but some one else was crucified instead.
Some say was a woman in 10 % so they have rest to use her energy and colours and woman was crucuifed but they all survived but as they were homosexual they used the crucified woman as slave and swapped her for a spoiled woman who was homosexual or at least bisexual to help them cover up "things" and her feminine energy in there bodies was helpful and made them feel good and beautiful and she felt horrid.
Ofcourse those who say such things in books etc keep low profile as they may be attacked and bashed by mobs of christians and muslims.