(fix): add comment and check

Author: ilan-gold

src/zarr/core/buffer/cpu.py

@@ -154,7 +154,8 @@ def create(
         order: Literal["C", "F"] = "C",
         fill_value: Any | None = None,
     ) -> Self:
-        if fill_value is None or fill_value == 0:
+        # np.zeros is much faster than np.full, and therefore using it when possible is better.
+        if fill_value is None or (isinstance(fill_value, int) and fill_value == 0):
             return cls(np.zeros(shape=tuple(shape), dtype=dtype, order=order))
         else:
             return cls(np.full(shape=tuple(shape), fill_value=fill_value, dtype=dtype, order=order))