The pageview dumps at http://dumps.wikimedia.org/other/pagecounts-all-sites/ are meant to follow the spec set out at http://dumps.wikimedia.org/other/pagecounts-all-sites/README.txt

Instead, it appears that for (presumably, zero-rated) requests, we're ending up with lang_code.zero instead of lang_code.project_variant. The hive query that generates these should be checked and fixed; I'll send an advisory to analytics-l to let third-parties know.