While trying to get the tests to pass, I ran into a small complexity regarding what kind of exception to raise if the iterables don't match lengths. As mentioned above, the implementation delegates to zip_equal(), which raises UnequalIterablesError. However, for python>=3.10, zip_equal() also emits a DeprecationWarning. To avoid this warning, the implementation delegates directly to zip() if possible. However, zip(strict=True) raises ValueError instead of UnequalIterablesError.

I decided to handle this by updating the documentation to state that zip_broadcast() raises ValueError. UnequalIterablesError is a subclass of ValueError, so this is true for all versions of python. I also note that the specific exception raised in older versions of python is UnequalIterablesError.

I think this approach is consistent with the idea of phasing out zip_equal() for python >=3.10, but it also breaks backwards compatibility very slightly. Let me know if you'd rather just raise UnequalIterablesError for all versions of python.

Thanks for the PR. I merged a combination of your version and mine that passes tests. I also worked around the deprecation warning such that 3.10 can raise UnequalIterablesError without version detection.