I think you're missing the fact that in the C version you have to write a specialized selector function each time (to find the thing you want to zap), whereas the macro works generically on any place. ("Place" here is an abstraction meaning "settable thing" that is closely related to Lisp macros and is analogous to the left-hand-side of assignment statements in most languages, but far more manipulable by the programmer.)
PG asked "How do you implement that in a language without macros?". I responded with a simplest translation of the example, but a more general solution exists too. Nothing stops me from using GObject instead of void*, which can provide named "places" and as much generic functionality as needed. `selector` and `action` can even operate on property tables, which would be a closer translation from lisp.
I was simply surprised that PG asked about something like that - I still think it's pretty simple and the code in C is as close to the macro as possible (with whatever object abstraction you need).
However I have to admit that I thought about other languages now and it seems that the described zap() is not possible in python... and that's interesting / worrying:
action(object[place])
cannot assign a new value to `object[place]`, while
