Board Thread:Support Requests - Getting Technical/@comment-24741716-20160327095350/@comment-26143371-20160327154354

Interlanguage links have to be requested separately for every combination of languages. While the en<-->zh link was requested at some point in the past, the others probably weren't.

You can request the links for en<-->es and es<-->zh (and others if required) at Community Central:Interlanguage link requests.