I personally ordered from ZW (ZWO) a few years ago, and I see no reason for problems. Shipping to the US takes a few days. It depends on what shipping method you choose. I'd recommend UPS shipping. You can choose UPS Shipping if you want a cheaper shipping cost.
When the package arrives at your local UPS, the courier will hand the package over to your post office. For more certainty, you can track your parcel via sendungsverfolgungpost.de. This is very convenient because the map clearly shows how much distance remains covered by the delivery.
