When Ive used attak or cavalier resin zimmerit, I always place the zimmerit first and then add the etch. But these are designed so that the etch has location areas imprinted in the resin as well.
In reality, the fixtures for the tools were in place before the zimmerit was added, and theres many clear images where you see that zimmerit does not completely fill out all the small recesses in the tool fixtures. If I was in your shoes, I would add the fixtures ... frames, pipes etc. ... then add the zimmerit, then add the actual tools ... exactly how its done in reality. NOTE: Ive never made my own zimmerit so Im not speaking from experience.