Zamioculcas zamiifolia stores water in thick, potato-like rhizomes just under the soil line. That single fact explains almost everything about how to keep one alive.
Because the plant is carrying its own reserve, watering on a fixed weekly schedule is the most common way to kill it. A ZZ in a normal-sized pot, in an average indoor room, often only needs water once every three to five weeks — less in winter, when growth all but stops. The right test isn't the calendar, it's the soil: let it go fully dry, then water thoroughly and don't touch it again until it's dry all the way through.
Yellowing stems are almost always a symptom of overwatering, not underwatering — the instinct to water a droopy or yellowing ZZ is exactly backwards. If a stem at the base goes soft or mushy, that's rhizome rot, and it usually means the pot has been sitting wet.
Light is flexible. ZZ plants tolerate low light better than almost any common houseplant, which is why they show up in windowless offices, but they'll grow noticeably faster in bright indirect light without needing it.
One more thing worth knowing: every part of the plant is mildly toxic if chewed or ingested, which matters if pets or small children are around it.