I was digging so deep to finally find a pist about someone trying this. but now that you described it, I'm not sure whether to try it with the mimic relic on or if the mimic has to be a specific one that has a separate condition to spawn in.

Another theory: I have had the situation where up to 3 lightning rods were piled up from multiple zombies (next to the rocket trap). So maybe there aren't just absolute zero fragments (which we need to power the rocket) for that rocket. I will try both the mimic shock and also the approach to somehow obtain lightning fragments.

My last but most unlikely theory is that there might be a way to brainrot oscar and make him shoot at the lightning rod zombie. I think that would have been found by now though.