Ovaj kruh je izvana hrskav, a iznutra mekan.

Because kruh is a masculine singular noun, and ovaj is the masculine singular nominative form of this.

• ovaj = this (masculine)
• ova = this (feminine)
• ovo = this (neuter)

Since kruh is masculine, the demonstrative has to agree with it:

• ovaj kruh = this bread

This is normal agreement in Croatian: the demonstrative, adjective, and noun must match in gender, number, and case.

Kruh is in the nominative singular because it is the subject of the sentence.

The basic structure is:

• Ovaj kruh = subject
• je = is
• izvana hrskav, a iznutra mekan = what is being said about the bread

So the sentence literally works like:

• This bread is crispy on the outside and soft on the inside.

Since the bread is the thing being described, it stays in the nominative.

They are adverbs meaning:

• izvana = on the outside / from the outside / externally
• iznutra = on the inside / from the inside / internally

In this sentence:

• izvana hrskav = crispy on the outside
• iznutra mekan = soft on the inside

These words are very useful for physical descriptions:

• Kuća je izvana bijela. = The house is white on the outside.
• Jastuk je iznutra mekan. = The pillow is soft inside.

They are not changing form here; they stay the same.

Because they are adjectives describing a masculine singular noun: kruh.

So the adjective forms must match kruh:

• kruh = masculine singular
• hrskav = masculine singular
• mekan = masculine singular

If the noun changed gender, the adjectives would change too:

• Ova lepinja je izvana hrskava, a iznutra mekana.
  = This flatbread is crispy outside and soft inside.

• Ovo pecivo je izvana hrskavo, a iznutra mekano.
  = This pastry is crispy outside and soft inside.

So the ending is all about agreement.

Because Croatian often expresses this idea with a single adverb instead of a longer phrase.

English says:

• on the outside
• on the inside

Croatian can simply say:

• izvana
• iznutra

So you do not need a separate equivalent of on the here.

There are longer alternatives, but they sound heavier:

• s vanjske strane = from the outer side
• s unutarnje strane = from the inner side

In everyday speech, izvana and iznutra are much more natural in this sentence.

A is used here to show a contrast or a comparison between two different qualities:

• izvana hrskav, a iznutra mekan
  = crispy on the outside, while soft on the inside

If you used i, it would just mean and, without the same contrastive feel.

So:

• a = and/but/while, with contrast
• i = plain and

Since crispy outside and soft inside are contrasting qualities, a is the most natural conjunction here.

Because a is joining two coordinated parts with a contrast:

• Ovaj kruh je izvana hrskav, a iznutra mekan.

In standard Croatian, it is normal to put a comma before a in this kind of sentence.

You can think of it as separating:

1. Ovaj kruh je izvana hrskav
2. (ovaj kruh je) iznutra mekan

The subject and verb are not repeated in the second part, but they are understood.

Yes. Croatian often omits repeated words when they are obvious.

The full version would be:

• Ovaj kruh je izvana hrskav, a iznutra je mekan.

That is grammatically possible, but the shorter version is more natural here:

• Ovaj kruh je izvana hrskav, a iznutra mekan.

So the second je is simply left out because it is easy to understand from the first part.

Yes, Croatian word order is fairly flexible, although some versions sound more natural than others.

The given sentence is very natural:

• Ovaj kruh je izvana hrskav, a iznutra mekan.

You could also hear:

• Kruh je izvana hrskav, a iznutra mekan.
• Ovaj je kruh izvana hrskav, a iznutra mekan.

The meaning stays basically the same, but the emphasis changes a little.

For a learner, the original version is a very good neutral pattern to remember.

Yes. Hrskav is a common and natural Croatian adjective for food that is crispy or crunchy.

Examples:

• hrskav kruh = crispy bread
• hrskavi krumpirići = crispy fries
• hrskava korica = crispy crust

You may also see related forms depending on gender and number:

• hrskava
• hrskavo
• hrskavi, etc.

So hrskav is exactly the kind of word you would expect in a sentence about bread.

Yes. Mekan is the normal adjective for soft in many everyday contexts.

Examples:

• mekan kruh = soft bread
• mekan jastuk = soft pillow
• mekana tkanina = soft fabric

Like other adjectives, it changes to match the noun:

• masculine: mekan
• feminine: mekana
• neuter: mekano

So in this sentence, mekan matches masculine singular kruh.

Because this sentence is in standard Croatian, where kruh is the normal word for bread.

Other South Slavic varieties use different common words:

• kruh = standard Croatian
• hljeb = common in Bosnian / Montenegrin / some Serbian usage
• hleb = standard Serbian

So if you are learning Croatian specifically, kruh is the form you should learn.

The main changes would be in ovaj and the adjectives.

For a feminine noun:

• Ova pita je izvana hrskava, a iznutra mekana.
  = This pie is crispy on the outside and soft on the inside.

For a neuter noun:

• Ovo pecivo je izvana hrskavo, a iznutra mekano.
  = This pastry is crispy on the outside and soft on the inside.

So the pattern stays the same, but agreement changes:

• ovaj / hrskav / mekan for masculine
• ova / hrskava / mekana for feminine
• ovo / hrskavo / mekano for neuter

It is a natural Croatian sentence.

Croatian often describes food this way:

• izvana
  • texture/appearance
• iznutra
  • texture/appearance

So saying:

• izvana hrskav, a iznutra mekan

is very idiomatic and sounds like something a native speaker would genuinely say about bread, pastry, pizza crust, and similar foods.