You should never flip your Zinus mattress, but you should rotate it. With the exception of one specific model sold in New Zealand, all Zinus mattresses are made with one side for comfort and the other for support.
Sleeping directly on the support side may cause discomfort or worse, bodily harm.
However, it is a good practice to regularly rotate the head and foot of your Zinus mattress to allow for wear and tear to build more evenly across the mattress.
