I think honestly, the best answer is to let the cells rest awhile and then measure the open circuit voltage with a voltmeter. With every NiMH cell I own I can calibrate the voltage with the state of charge once I am familiar with the characteristics of that kind of cell. Nickel zinc cells have characteristics closer to Li-ion (CC/CV charge algorithm), so open circuit voltage should be an even better indication. Just measure a few cells that are fully charged, 3/4 charged, 1/2 charged, 1/4 charged, etc. and get a feel for what voltage they have.
The MTS MBT-1 tester includes a pad that's dedicated to lithium primary AA cells. Wouldn't a NiZn's voltage and other characteristics be close enough? At least that's what I'm hoping, having just ordered a dozen NiZn AAs.
I just gave ZTS a call and they said that they have not examined the new batteries yet. I may be a year before they run their tests for inclusion in their testers. This was an estimate only, not a promise.
I also emailed PowerGenix and will have to see what they say.
I test my NiZn AA cells by setting my MAHA C-9000 charger to "Discharge > 1000mA" and watching the display. I own 11 NiZn AAs, and using this method, typically 7 will begin at 1.65 or 1.66V under a 1A load, the rest at 1.69 to 1.71V. All will drop about 0.1V every 10 seconds until settling in at 1.61-1.62V or 1.65-1.67V.