Zamioculcas zamiifolia, commonly known as a ZZ plant, is a tropical perennial aroid meaning it is related to Arums and Philodendrons. It is an extremely low maintenance plant with no real pests, thriving in partial shade outdoors with bright indirect light to low light indoors. The requirements for a happy Zamioculcas zamiifolia are few but finite so if your plant is suffering or dying, the causes can easily be remedied given the plant is not too far gone. You need to avoid direct sun, avoid root bind, and have it in only rich well-drained soil. (Wet soil will cause it to yellow, drop the leaves, and rot the roots.)
Inspect the plant carefully, and using pruning shears, cut away any damaged or diseased leaves and stalks. Cut stalks down to the base of the plant if necessary. Discard these cuttings into the waste bin and not the compost pile, to avoid the spread of disease.
Slide your ZZ plant gently out of its pot. Loosen the roots so that they are not girdling the root ball and will grow in an outward direction. Release any old soil from the root ball and set it aside briefly.
Mix up a fresh batch of well drained soil for your ZZ plant with three parts good quality potting mix and one part sharp sand or builders sand to increase drainage capabilities. Fill a shallow pot with drainage holes partially full with the new soil mix. For outdoor ground plantings, dig in a few pounds of sharp sand into the soil with a hand trowel or shovel.
Slide the ZZ plant into the new pot or ground location, gently splaying the roots throughout the soil. Ensure that the soil level stays consistent on the stems of the plant. Fill soil in around the roots, pressing gently with your palm to lightly compact. Water in well til consistently moist but not soaking wet.
Water your ZZ plant when it feels dry about an inch down into the soil. Over-watering is detrimental to the ZZ than slightly dry conditions.
Fertilize your Zamioculcas zamiifolia once a year with a good quality water soluble fertilizer in liquid form or in slow release encapsulated form such as osmacote.