I've always pronounced it like "hazel", but many of my colleagues rhyme it with "dazzle".
The Bazel website even has an FAQ entry about it, but they managed to completely confuse the issue:
> How do you pronounce “Bazel”?
> The same way as “basil” (the herb) in US English: “BAY-zel”. It rhymes with “hazel”. IPA: /ˈbeɪzˌəl/
Little problem here... Basil, the herb, can be pronounced either like hazel or like dazzle. Or even rhymed with hassle!
So naturally I opened a PR attempting to clarify this. It led to an interesting discussion, and in the end I wrote a bad poem acknowledging both pronunciations: