As far as concerns 0 being a defined quantity, of course it's defined...in the syntax of arithmetic. Without an underlying conceptual syntax, it would be undefined...and the absence of syntax is what UBT is all about.
Where something is undefined due to its lack of expressive syntax, it is totally unmeasurable even in principle. Therefore, there are no extensional or durational distinctions to be made, and this means that for practical and theoretical purposes, extension and duration are zero.
In fairness to Parallel, he seems to attempt to specify a paradox when he opines that "the undefinable" cannot have well-defined properties such as “unbound”, “without restraint”, and “zero extension and duration”. But this attempt is a bit hard to figure, since if the property "undefinable" is well-enough defined to be contradicted by the properties “unbound”, “without restraint”, and “zero extension and duration” as Parallel maintains, then it is well-enough defined to be described by them as well, particularly with respect to a model involving syntactic and presyntactic stages. Because Parallel does not take account of such a model, he can't be talking about the CTMU. What Parallel is talking about, only he knows for sure.