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This could mean that the potting mix that they are in doesn't contain enough nutrients. You can add compost, or fertilizers and this can help to kickstart them into gear.

This should only be done if you are completely certain that these are well rooted cuttings, as this is typical behavior of a plant that has not finished rooting. Feeding with fertilizers at this stage will kill off the newly forming roots, so it is important to make sure that these are well rooted.

A ZZ plant can reach a height of 5 feet

I recommend leaving it as is. If you must do something about it, then I would suggest repotting it into a bigger area.

Here is an article that will give you more information on their care:https://www.gardeningknowhow.com/houseplants/zz-plant/caring-for-zz-plant.htm

It is very important the plant be in fast draining soil which is sandy. Cactus soil is a good choice. They don't like wet roots.

https://www.gardeningknowhow.com/houseplants/zz-plant/caring-for-zz-plant.htm

Do you mean that they are pulling up out of the soil, or that they are showing above the soil line?
If the soil is low in the pot you can top off the soil with some fresh potting mix.

It isn't necessary, but if you did want to trim at all to help conserve moisture loss, then just cut the tips of the leaves of the older growth. Leave new leaves and growth alone to continue to mature. Do you know if these have rooted yet, or are these fresh cuttings?