Two years ago I purchased one the these plants...and it looks so healthy that it almost looks artificial...it gets hi indirect light...moderate watering...has very dark green healthy looking leaves. When/what triggers it..to start growing and producing new foliage? As I said it looks incredibly healthy but does nothing..I have tried fertilizing and no change.
I've never had one of these, the they (ZZ plants) are know as the simplest, no-brainer plants to grow. My guess would be simply to pot it up one size and give it some room to grow. Sound like an idea?
I bought one around March. It's put out two new shoots. From what I understand, the tuber(s) have to be well formed. Even then you'd be lucky to get one or two new shoots per year. This is based only on what I've read though. Light does help though and so does watering it at least every 3 - 4 weeks when it's warm. Not necessarily practical knowledge.
