> Of specific note, many people have attempted to write a grammar (parser) for zonefiles and it is almost impossible.

I had to build a DNS zone file parser +3 years ago for the web application firewall that I was building for my employer. I have to agree that I had a lot of problems implementing the different formats but ultimately — implementing the most common ones — succeeded. The project later became the CDN of one of the biggest hosting providers in the US, and as far as I know, there hasn't been any problems with the configuration files.

BIND zone files are (for the most part) very straightforward.