UPDATE Though the C source does not indicate version, the phpinfo does give the zep version used (0.9.2a-dev). Sorry for not spotting that previously.
Trying to regenerate phalcon 2.0.10 with zephir fails. The phalcon.c file saysThis file was generated automatically by Zephir do not modify it but not which version of zephir was used. Using zephir stable (0.8.0) to build phalcon stable (2.0.10) produces two syntax errors:
Zephir\ParseException: Syntax error in /usr/local/src/cphalcon-phalcon-v2.0.10/phalcon/paginator/adapter/querybuilder.zep on line 168
      var groups = totalBuilder->getGroupBy();
    ----------------------------^and
 Zephir\ParseException: Syntax error in /usr/local/src/cphalcon-phalcon-v2.0.10/phalcon/paginator/adapter/querybuilder.zep on line 170
       var groupColumn = implode(", ", groups);
    ----------------------------^Can 2.0.10 be generated with the stable zephir 0.8.0a or only with an unstable one, and if the latter, exactly which version of zephir was used to produce the C code in the released 2.0.10? Without knowing this it's not possible to augment phalcon with certainty that the only changes to the resultant C code are from changes made to zep files.