Implementing AirPrint with DNS-SD
Caveats: I don't own an AirPrint device nor do I have one available elsewhere for testing. So I'm not talking from my own experience in the following answer...




First, when publishing a printer (AirPrint or not) from a DNS server ("static, Wide Area Bonjour"), you should include ALL of the TXT record key/value pairs which are listed in the current Bonjour Printing specification.

A tabular overview is listed in chapter 9 of the specification document (for all details please read the complete chapter):


Second, the Bonjour Printing specification requires that for a printer you always have to register the LPD protocol (_printer._tcp), even if the device does not support it (port = 0) !.

The reason for this seemingly braindead requirement is this: LPD is considered the "flagship" protocol for service discovery related to printing. (Meaning: if you own the service instance name for _printer then you also own it for _pdl-datastream, _ipp, _ipps, etc.)

Some older versions of OS X enforced this. They would not work without it. Newer versions (and probably the next macOS version too) are less dogmatic and more pragmatic...

In your case the air (has nothing to do with AirPrint, but means s.th. like authentication information required), TLS, UUID, usb_MFG, usb_CMD and usb_MDL keys are missing (even if you'd use "" as their key values).
Third, please take to heart the general rule about the trailing dot for domain names. Details are outlined here: 


dns-sd.org/TrailingDotsInDomainNames.html

Fourth, maybe you also should enclose your key values in quotes. Example:

pdl="application/pdf,image/urf"


not

pdl=application/pdf,image/urf

Fifth, in general, what is quoted above in the OP code block does not look like a valid format for a zone file to me. (I notice that the original question has been edited by other people than the OP, so I won't comment on the details...)