In this page: https://www.freebsd.org/doc/en_US.ISO8859-1/books/porters-handbook/uses-zope.html ,the www/zope link pint to http://www.freebsd.org/cgi/url.cgi?ports/www/zope/pkg-descr,but there is no such port named www/zope. I see the Mk/Uses/zope.mk, it use www/zope213 now. It is better to make www/zope a plain text instead of a link so it will no need to change the version when zope updated.
A commit references this bug: Author: mat Date: Fri Aug 4 13:42:25 UTC 2017 New revision: 50634 URL: https://svnweb.freebsd.org/changeset/doc/50634 Log: Replace the package with a filename, zope versions changes often. PR: 220405 Reported by: amutu amutu com Sponsored by: Absolight, The FreeBSD Foundation Changes: head/en_US.ISO8859-1/books/porters-handbook/uses/chapter.xml
Right, I removed the link