En tiu kazo uzu la zipon.

Yes. Uzu is the -u verb form, which Esperanto uses for commands, requests, suggestions, and instructions.

• uzi = to use
• uzu = use! / please use / should use

So uzu la zipon means something like use the zip or use the zipper.

Compared with English, Esperanto does not use a separate bare verb form for commands. Instead, it uses the special ending -u.

Examples:

• Manĝu! = Eat!
• Venu! = Come!
• Legu la libron. = Read the book.

The -n marks the direct object.

In uzu la zipon, the thing being used is the zip, so it gets -n.

Breakdown:

• la zipo = the zip
• la zipon = the zip, as the direct object

This is one of the most important uses of -n in Esperanto. The direct object is the noun directly affected by the verb.

More examples:

• Mi vidas la hundon. = I see the dog.
• Ŝi aĉetis libron. = She bought a book.
• Uzu la zipon. = Use the zip.

Because en here shows location or situation, not movement into something.

• en tiu kazo = in that case
• en tiun kazon would suggest movement into that case/situation, which is not what is meant here

In Esperanto, after prepositions like en, you normally do not use -n unless there is a directional idea.

Compare:

• Mi estas en la domo. = I am in the house.
• Mi iras en la domon. = I am going into the house.

Here, en tiu kazo is an idiomatic expression meaning in that case, so no accusative is needed.

Because tiu is used for a specific noun, while tio stands alone as a pronoun.

Here the noun is kazo:

• tiu kazo = that case

So:

• tiu = that one / that (before a noun)
• tio = that (thing), standing by itself

Compare:

• Tiu libro estas bona. = That book is good.
• Tio estas bona. = That is good.

Since kazo is actually stated, Esperanto uses tiu, not tio.

It is a prepositional phrase meaning in that case.

Structure:

• en = in
• tiu = that
• kazo = case

So literally it is very close to English: in that case.

It functions as a sentence adverbial: it gives the condition or situation under which the instruction applies.

You could think of the whole sentence as:

• In that situation, use the zip.

La is the definite article, meaning the.

So:

• zipo = a zip / zipper / zip fastener
• la zipo = the zip

Esperanto has only one article, la, and it does not change for gender, number, or case. The -n goes on the noun, not on la:

• la zipo
• la zipon

In this sentence, la suggests a specific zip that is already known from the context.

Yes, it is a normal Esperanto-style borrowing.

Esperanto often takes internationally familiar words and gives them regular Esperanto endings:

• noun ending -o
• adjective ending -a
• verb ending -i

So zipo is a noun formed in the standard way. Even if the original source is English or another European language, once it takes an Esperanto ending and behaves like a normal Esperanto word, it is grammatically just another Esperanto noun.

That means it can be inflected regularly:

• zipo = zip
• zipon = zip, as a direct object
• zipoj = zips
• zipojn = zips, as direct objects

Yes, Esperanto word order is fairly flexible, because endings show the grammar.

The neutral order here is:

• En tiu kazo uzu la zipon.

But other orders are possible for emphasis, for example:

• Uzu la zipon en tiu kazo.

Both are understandable. The original version puts en tiu kazo first, which sounds natural if you want to emphasize the condition first: in that case.

It is generally neutral.

The -u form can sound like:

• a direct command,
• an instruction,
• a recommendation,
• or a polite procedural step,

depending on context.

So uzu la zipon might mean:

• a firm command: Use the zip.
• an instruction in a manual: Use the zip.
• a suggestion: In that case, use the zip.

Esperanto itself does not force one exact tone here; the context determines how strong it sounds.