I don't know of any reason that ZMA cannot be taken with food, during the day, or anything else.
I mean, it's simply zinc, magnesium, and B6. It is correcting deficiencies.
Unless I saw a study that showed specific effects of a ZMA combo taken on an empty stomach before bed showed better effects than the same combo taken at various times during the day with/without food, I don't see any reason for concern.
Zinc by itself on an empty stomach can often cause nausea, sometimes to the point of vomiting.