WOW!! Six years between messages? Seem like just yesterday.
A couple of points should be touched on here. The first having to do with shrinkage. ZR being 54% solids by volume will shrink 50% during the drying phase thus shrinking down into any surface defects telegraphing any sanding scratches thru the final finish. If that isn't going to be a problem you may apply your top coat almost wet on wet and allow the two to cure out together.
If shrinkage and telegraphing will be a problem, allow the ZR thirty days to achieve full shrinkage and build your sandable sytem on top of the fully cured ZR film. Fully cured ZR should have no adverse reaction to subsequent coatings. If there were to be a reaction, it would happen more NOW than LATER.
