Notice how I did not quote the "Customer must be at least 18 years old to use the Service" part. That sentence is completely non-problematic. The part that's a problem is the part I actually quoted:

    By agreeing to these Terms, Customer represents and warrants to Zed that: (a) Customer is at least 18 years old

The "Terms" is earlier defined to mean:

    these Terms of Service, the Data Processing Addendum (“DPA”), available upon request, and Zed’s Privacy Policy

So the Terms you have to agree to in order to download the editor, clearly state that by agreeing to the Terms, you warrant that you're 18+. ("Customer" is defined to be a synonym for "You", FWIW).