I've taken ZMA for several months straight when not oncycle. It's part of my regular suppliment regiment. I've found that I frequently sleep less time when taking ZMA but sleep more restfully than if I slept for 11 hours straight. I love the stuff. My girlfriend had trouble sleeping and I told her to try taking 2 before sleeping (with no food or pills for the next 30 minutes following taking it, and nothing for 1 hour beforehand). She says that she sleeps much better now. She used to get so tired she could barely stay awake by like 9PM. Now she is able to stay alert past 11PM if need be (she wakes up at 5AM every weekday).
Honestly I don't think it's the ZMA that's making it hard for you to sleep.