I received one, and it has no roots. How do I plant it and in what?
You have a 'cutting' from a plant that yes, can be rooted.
You can cut the leaf stem to about 3 or 4 inches and give the stem a fresh cut at a slant.
Place it in a glass of fresh water and locate it in a bright location but away from direct sunlight.
Top off the water when it gets low so that the new roots do not come out of the water.
You can also place the cutting in a small 3" pot of potting mix.
Dip the end of the stem in rooting hormone and place the stem in the soil and tamp it down.
Bright location and keep the soil moist.
Though ZZ plants are easy to grow they are very slow to propagate.