csubich

One difference appears to be that ZipStore and FsspecStore views of the file don't present the same set of keys: ```python zipstore = zarr.storage.ZipStore('bad.zipstore.zip',mode='r') zipstore._sync_open() # Work around zarr bug...

If it were a concurrency bug, then I'd expect it to also happen with non-dask writes to the ZipStore. In the maximal code where I discovered the bug (by way...

I was hoping that the parallelism hint would work out, but the current version's `ZipStore.set()` [takes a lock](https://github.com/zarr-developers/zarr-python/blob/6811c9483a86a0e5c835b4f3c3a2dd09254c38e5/src/zarr/storage/_zip.py#L220) before calling `_set()` which performs the write, and 2.16.1's `ZipStore.__setitem__` [does essentially...