U zoološkom vrtu nema zeca ni lisice, ali moja nećakinja svejedno želi vidjeti leptire.

Because u can take different cases depending on meaning:

• u + accusative = motion into somewhere
• u + locative = being in somewhere

Here the sentence means in the zoo, not into the zoo, so Croatian uses the locative:

• zoološki vrt = zoo
• u zoološkom vrtu = in the zoo

Both words change into the locative:

• zoološki → zoološkom
• vrt → vrtu

Nema means there is no / there are no / does not have, depending on context.

In this sentence:

• U zoološkom vrtu nema zeca ni lisice
  = There is no rabbit or fox in the zoo
  or more naturally, The zoo has no rabbit or fox

It is the negative form related to ima:

• ima = there is / there are / has
• nema = there is not / there are not / does not have

A very important grammar point is that nema usually requires the following noun to be in the genitive.

Because after nema, Croatian normally uses the genitive case.

So:

• zec → zeca
• lisica → lisice

That is why the sentence says:

• nema zeca ni lisice

not:

• nema zec ni lisica

This is a very common pattern:

• Ima psa. = There is a dog.
• Nema psa. = There is no dog.

Here ni means something like nor or not even ... or ... in a negative structure.

So:

• nema zeca ni lisice
  literally: there is no rabbit nor fox

In natural English, you would usually say:

• there is no rabbit or fox
• there are neither rabbits nor foxes

Because the sentence is already negative with nema, Croatian often uses ni to continue that negative idea.

Croatian often uses the singular after nema when talking about the absence of a type of animal or thing.

So:

• nema zeca ni lisice

can still sound natural even if English might prefer:

• there are no rabbits or foxes

Croatian singular here is not necessarily about exactly one rabbit and one fox. It can simply refer to those animals as types present in the zoo.

Plural would also be possible in some contexts, but the singular is very normal.

Ali means but.

It connects two contrasting ideas:

• There is no rabbit or fox in the zoo,
• but my niece still wants to see butterflies.

So ali introduces the contrast between what is missing and what she wants anyway.

Moja nećakinja means my niece.

It is in the nominative case because it is the subject of the second clause:

• moja nećakinja svejedno želi vidjeti leptire
• my niece still wants to see butterflies

Breakdown:

• moja = my
• nećakinja = niece

Both are in feminine singular nominative:

• moja agrees with nećakinja

Svejedno here means anyway, all the same, or still.

So:

• moja nećakinja svejedno želi vidjeti leptire = my niece still wants to see butterflies anyway

It shows that the second part is true despite the first part. Even though there is no rabbit or fox, she still wants to see butterflies.

Do not confuse this use with another common meaning of svejedno:

• Svejedno mi je. = I don’t mind / It’s all the same to me.

Here, though, it means nevertheless.

Because Croatian often uses:

• a conjugated verb of wanting, being able, having to, etc.
• plus an infinitive

So:

• želi = wants
• vidjeti = to see

Together:

• želi vidjeti = wants to see

This works much like English:

• She wants to see butterflies.

There is no extra word equivalent to English to before vidjeti in the sentence, because vidjeti itself is already the infinitive form.

Vidjeti is the standard infinitive of to see.

The main forms are:

• vidjeti = to see
• vidim = I see
• vidi = he/she sees

Croatian verbs can have infinitives ending in -ti or -ći, and sometimes the stem changes too. So you often need to learn the infinitive as a vocabulary item.

In this sentence, želi vidjeti is the normal standard form.

Because leptire is the accusative plural, and it is the direct object of vidjeti.

• leptiri = butterflies (nominative plural)
• leptire = butterflies (accusative plural)

Since the niece wants to see butterflies, butterflies are what she wants to see, so Croatian uses the object case:

• želi vidjeti leptire

This is especially noticeable because leptir is masculine animate, and masculine animate nouns usually have:

• nominative plural in -i
• accusative plural in -e

They are doing different jobs in the sentence.

• zeca and lisice come after nema, which often uses the genitive, and singular is common when naming kinds of animals not present.
• leptire is the direct object of vidjeti, so it is in the accusative plural because she wants to see butterflies.

So the difference is caused by both:

1. different grammar roles
2. different number chosen by the speaker

Croatian word order is more flexible than English, though not completely free.

The given sentence is very natural:

• U zoološkom vrtu nema zeca ni lisice, ali moja nećakinja svejedno želi vidjeti leptire.

You could move some parts for emphasis, for example:

• Moja nećakinja svejedno želi vidjeti leptire.
• Svejedno moja nećakinja želi vidjeti leptire.

But the original order sounds smooth and neutral.

The first clause begins with the location u zoološkom vrtu, which is very natural when setting the scene.

Yes, that is close to the structure of the Croatian sentence, but it sounds less natural in English.

A more natural English translation would be something like:

• There is no rabbit or fox in the zoo, but my niece still wants to see butterflies.
• The zoo has no rabbit or fox, but my niece still wants to see butterflies anyway.

So the Croatian structure can be followed quite closely, but good English usually rearranges it a little.

Yes. Word for word:

• zoološki = zoological
• vrt = garden

But as a fixed expression, zoološki vrt simply means zoo.

So although the literal meaning is zoological garden, in normal translation you should just say zoo.

The dictionary forms are:

• zoološki vrt = zoo
• zec = rabbit / hare
• lisica = fox
• nećakinja = niece
• leptir = butterfly

The sentence uses changed forms because of case:

• vrt → vrtu
• zec → zeca
• lisica → lisice
• leptir → leptire

This is very typical in Croatian, so it is useful to get used to identifying the base form behind the ending.