Это главный приоритет и зона ответственности.

In Russian, the present-tense verb to be is usually omitted.

So:

• Это главный приоритет и зона ответственности.

literally looks like:

• This main priority and area of responsibility.

but it naturally means:

• This is the main priority and area of responsibility.

This is completely normal in Russian. In the present tense, Russian often just puts the two parts of the sentence next to each other without a verb.

Это usually means this or that, depending on context.

In a sentence like this, it often works almost like this is:

• Это главный приоритет = This is the main priority

It points to something already mentioned, already known, or physically indicated.

So это is the element that introduces what something is.

They are in the nominative case.

Why?

Because this is a basic identification/equational sentence:

• Это главный приоритет
• Это зона ответственности

Both noun phrases name what это is, so nominative is expected here.

You can think of them as the predicate nouns of the sentence.

Because главный only agrees with приоритет, not with зона.

• приоритет is masculine, so: главный приоритет
• зона is feminine, so if главный modified it, it would have to be главная зона

In the actual sentence:

• главный приоритет и зона ответственности

the adjective главный belongs only to приоритет.

So the structure is:

• [главный приоритет] и [зона ответственности]

not:

• [главный] [приоритет и зона]

If you want main to describe both nouns, you would usually repeat the adjective:

• Это главный приоритет и главная зона ответственности.

Because Russian often uses a noun + genitive noun to express of relationships.

Here:

• зона = zone / area
• ответственности = of responsibility
  (genitive singular of ответственность)

So:

• зона ответственности = zone/area of responsibility

This is a very common Russian pattern:

• центр города = city center / center of the city
• чашка чая = cup of tea
• уровень жизни = standard of living

So ответственности is in the genitive because it depends on зона.

Yes, very much so.

Зона ответственности is a common expression in business, management, politics, and official speech. It means:

• area of responsibility
• sphere of responsibility
• what someone is responsible for

So this sentence sounds natural in formal or professional Russian.

Depending on context, English might translate it in several ways:

• This is the main priority and area of responsibility.
• This is the top priority and the relevant responsibility area.
• This is the main priority and part of their remit.

Yes, it is natural Russian.

Even though English speakers sometimes feel that main priority or top priority is a bit repetitive, Russian very commonly uses:

• главный приоритет
• основной приоритет

It simply means:

• main priority
• top priority

So this is normal usage, especially in formal or public language.

Because after это in this kind of identifying sentence, Russian normally uses the nominative, not the instrumental.

So:

• Это зона ответственности. = This is an area of responsibility.

That is the standard pattern.

The instrumental is common in other sentence types, especially with forms of to be in the past/future or in some stylistic structures, but here nominative is the normal choice.

You know from context, because Russian does not have articles like a and the.

So главный приоритет could in theory be rendered differently in English depending on the situation. But in most contexts:

• главный приоритет → the main priority

sounds the most natural.

That is because main usually makes the noun feel specific and definite.

The same applies to зона ответственности. Depending on context, English may need:

• the area of responsibility
• an area of responsibility
• just area of responsibility

Russian leaves that choice to the context.

Yes, Russian word order is flexible, though the emphasis changes.

For example:

• Это главный приоритет и зона ответственности.
  Neutral statement.

You could also say:

• Главный приоритет и зона ответственности — это ...

if you want to put that noun phrase first and then explain what it refers to.

Or:

• Это зона ответственности и главный приоритет.

if you want to foreground зона ответственности first.

So the original order is natural, but not the only possible one. Word order in Russian often reflects emphasis more than strict grammar.