I'll agree and say they are difficult to blend! It has happened historically and, as someone Rich replied, all faiths have some dimension of another faith within them--Zen wouldn't be Zen without Taoism---Christianity wouldn't quite be what it is if it hadn't had contact with the endless amount of faiths that spanned Europe and the Middle East as it grew--etc.
I agree, there's absolutely some contradictions in faiths when they're looked at face value, and in the depths as well. I think there are ways to do it without patronizing both traditions, by seeing the deep implications, critiquing and so forth with the traditions. It takes quite a "religious practice" if you will, to do it, in my opinion.