Of the 6 zoeas I found, at least 3 survived to transform. They really really like to hide, so it's difficult to tell whether I'm seeing the same 3 shrimp or if they all 6 lived and I only see 3 at once. They are now, roughly 2.5 months later, approaching adult size and doing well. I've got another berried and she should be hatching out relatively soon. If the size of her brood is any evidence, it ought to be quite a few more than 6 zoeas.
The main reason I'm on here right now is an odd reaction that they've just had. I occasionally try feeding them small amounts of various foods, usually spirulina, but occasionally something like pulverized turnip greens or the like. Very rarely I'll give them something with a reasonable amount of protein, but they almost always ignore it (crushed fish flakes, for instance.)
Tonight I decided to try a couple of sinking fish pellets on them and the results were pretty amazing. I smashed two New Life Spectrum pellets and dropped them into the tank. The shrimp are now going insane, dancing everywhere, though they are completely disinterested in the food. Assuming they don't all die tonight or something like that, I'll try again in a couple of weeks and see if the reaction is due to the pellets or another factor. I'm very wary of post hoc reasoning, but I've not seen them this animated except immediately after a very stressful event. Additionally, I'm going to watch for berried shrimp, as that is something that is generally expected after an event like this. If I get several berried shrimp in the next few days, I'd consider that to be relatively good evidence for these pellets acting in the way that breeding drops are generally intended.
Any worthwhile conclusions would require multiple testing events, of course.