About [[Osm:Issues.show.reports/nl]]
This message cannot be translated. It keeps complaining about a syntax error due to the presence of the "zero" clause even though that is in the original message.
No, the order is completely correct (and chaing it would have no effect).
This is a known current bug of TWN, which no loger accepts the "zero" plural option for any language, because it restricts these options to only the numbered options for (default) plural rules of the language. It was valids in the past, but a change in TWN code caused this new caveat under a false assumption that extra values, than just option 1 for singular, and the last (implicitly numbered) option for default plural would be invalid.
But many messages in Mediawiki define specific values (such as "zero=", "one=", "99+=", or other numeric values like "10=", "100="); such cases occur as well in English, but are more frequent in languages that need additional context-specific rules than just the basic default rules).
Even languages that normally don't mark the grammatical plural have specific words or sentence forms in some cases (e.g. expressing zero by using a negated form or changing to another adjective or adding some extra particles). If we don't use these options, the only redering using digits only looks much less familiar and less friendly.
IMHO it's not to TWN to decide the maximum of forms that can be set with plurals (notably not for MediaWiki's {{PLURAL: value | alternate forms... | default form }}, but as well for plural rules used in Python, Java, Ruby or other languages, and i18n libraries such as ICU using CLDR data: if we specify "too many", these extra forms may be left unused by the target application but won't break the message: it must just provide at least the last default form; other forms will be used conditionally but using variable rules.
So TWN may just display a warning, allowing to reconfirm when saving again without other changes (the warning may just say that extra forms may be useless, and should as well send a warning if there are fewer forms than expected (notably in Slavic and Celtic languages or in Arabic, that have more than 2 forms)