You can email David at firstname.lastname@example.org or email@example.com, 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.