Etykieta zwrotna i przesyłka zwrotna są gotowe.

Because the subject is two things joined by i:

• etykieta zwrotna = return label
• przesyłka zwrotna = return shipment / return package

Together, they form a plural subject, so Polish uses:

• są = are
• gotowe = ready in the plural non-masculine-personal form

Both nouns are singular on their own, but as a pair they require a plural verb and plural adjective.

Polish plural adjective forms depend on the type of noun.

• gotowi is used mainly for masculine personal groups, especially people
• gotowe is used for:
  • feminine nouns in the plural
  • neuter nouns in the plural
  • mixed groups without masculine persons
  • objects/things

Here, etykieta and przesyłka are both feminine nouns and refer to things, so the correct form is gotowe.

Because it describes both nouns separately:

• etykieta zwrotna = return label
• przesyłka zwrotna = return shipment

In Polish, if you want to make it clear that the adjective applies to both nouns, repeating it is very natural.

If you said:

• Etykieta i przesyłka zwrotna są gotowe

this would most naturally sound like only przesyłka is explicitly modified by zwrotna, or at least it would be less clear. Repeating zwrotna avoids ambiguity.

Zwrotna means return, for return, or related to sending something back.

It comes from zwrot = return.

So:

• etykieta zwrotna = return label
• przesyłka zwrotna = return shipment / return parcel

It is an adjective, so it changes form to match the noun it describes.

Because zwrotna must agree with the noun it describes in gender, number, and case.

Both etykieta and przesyłka are:

• feminine
• singular
• here in the nominative case

So the adjective must also be feminine singular nominative:

• zwrotna

Compare:

• zwrotny = masculine singular
• zwrotna = feminine singular
• zwrotne = neuter singular or non-masculine-personal plural, depending on context

They are in the nominative case because they are the subject of the sentence.

The basic structure is:

• Etykieta zwrotna i przesyłka zwrotna = the subject
• są gotowe = are ready

So the nouns stay in their dictionary-like subject form:

• etykieta
• przesyłka

In a normal full sentence like this, yes.

Polish often omits to be in the present tense only in some very specific kinds of sentences, especially in equational sentences like:

• To mój brat. = This is my brother.

But with an adjective like gotowe, you normally say:

• Etykieta i przesyłka są gotowe.

Without są, the sentence would sound incomplete or unnatural in standard usage.

Because Polish does not have articles like English a/an/the.

So:

• etykieta can mean a label or the label
• przesyłka can mean a shipment or the shipment

The exact meaning depends on context. In this sentence, English would usually translate it as the return label and the return shipment are ready, but Polish does not need separate words for the.

Przesyłka is a fairly broad word. Depending on context, it can mean:

• shipment
• parcel
• package
• mail item

In logistics or customer-service contexts, przesyłka zwrotna usually means something like:

• return shipment
• return parcel
• returned package

The best English translation depends on the situation.

Yes. Polish word order is more flexible than English because grammatical endings carry a lot of information.

This sentence could be rearranged, for example:

• Etykieta zwrotna i przesyłka zwrotna są gotowe.
• Gotowe są etykieta zwrotna i przesyłka zwrotna.

Both are grammatical, but the neutral, most straightforward order is the original one.

The original sentence sounds like a standard informational statement: The return label and the return shipment are ready.

Then you would switch back to the singular forms.

For example:

• Etykieta zwrotna jest gotowa. = The return label is ready.
• Przesyłka zwrotna jest gotowa. = The return shipment is ready.

Notice the changes:

• są → jest
• gotowe → gotowa

That is because each subject is now a single feminine singular noun.