You can email David at email@example.com or firstname.lastname@example.org, which is a reliable way to reach him, but not the only way. David also responds to messages on YouTube and Facebook, depending on your preference. Facebook usually has the fastest response time. You can join the official Zul mailing list by clicking here.
You can also join one of David’s mailing lists at dvspress.com/list to stay up-to-date on his book publishing schedule and get free early access to all non-YouTube content.