A pest on zam zam plant.
It has removable scales with something brown under in the center. The leaves are very sticky, a couple are dark brown spotted on yellow leaves. When I look up pests of zz, computer says they don't exist!
Arapahoe County Colorado plant disease
Generally, there are not pests of Zamioculcas zamiifolia, however, it would depend on what other plants this particular one is close to and if it is infested with insects which may colonize the ZZ plant.
If you could provide a couple of pictures of the problem, it might be helpful in determining if this is indeed an insect.
The other plants are aloe Vera, Jade, and one I was told is a relative of Croton. None of them have these symptoms.
Based on the photos provided, I suspect this is a scale insect of some sort. This would be a phloem feeder because it is producing honeydew (insect poop) which is the stickiness on the leaves. Since the ZZ plants have such thick leaves, you can try cleaning the leaves with a cotton ball/swab soaked in Isopropyl alcohol (not sopping wet, but enough to remove the insects and honeydew). The thick leaves can generally tolerate this. I have done this with a Hoya plant before. This may need to be done once a week or every other week for 2 or three times in order to make sure that all the scale insects are removed.
Let me know if you have any other questions.