it was decided to use the zero rate of climb speed
Interesting, and understandable...
But I presume that demonstration requires the use of considerable power, as opposed to none. A 1.3Vs approach could obvioulsy be accomplished at zero thrust (all be it rather steep). Vzrc could not be demontrated power off, unless it were being flown at a speed determined during previous partial power flying?
So, instead of 1.3Vs, approach becomes 1.3Vzrc, power off, if that is the circumstance?