Slow growth in ZZ plants can result from insufficient light, improper watering habits (overwatering or underwatering), nutrient deficiency, compacted soil, or root rot. External factors such as environmental stress, temperature fluctuations, humidity levels, pests, diseases, transplant shock, and dormancy periods can also affect growth. To promote healthy growth, ensure optimal light conditions, establish a consistent watering schedule, provide balanced fertilization, improve soil aeration, and control pests and diseases.