How advisable is it to take zzzquil as a sleeping aid?

Depends. Zzzquil is an over the counter sleep aid. Diphenhydramine, aka benadryl, (diphenhydramine) is the primary active ingredient. It is not recommended if one has an allergy to any part of it. Side effects include dry mouth, urinary retention, dizziness, and blurred vision. There are other side effects. Care must be taken if one is taking prescribed medications. Always check with md before adding any new meds.