By accessing or using the Service, you (“You” or “Customer”) agree to these Terms of Service, the Data Processing Addendum (“DPA”), available upon request, and Zed’s Privacy Policy (collectively, the “Terms”).
If you are not eligible, or do not agree to the Terms, you may not access or use the Service.
pretty clearly again referring to only 'the Service' -- which does not include their website or app
If you do not agree to the Terms, you may not download or use the editor. The download page says that "by downloading and using the editor, you agree to the terms". If you aren't over 18, you can't agree to the terms.
except i'd still say that even if you "agree to the terms" most of them still apply conditionally upon using the service, and the language about 18 is also specifically about the service
> By agreeing to these Terms, Customer represents and warrants to Zed that: (a) Customer is at least 18 years old
"these Terms" are the terms you need to agree to in order to download the editor. You can't agree to them if you're under 18.