Ne razumijemo simbol, a kamoli cijelu kombinaciju.

A kamoli is an idiomatic expression meaning let alone, much less, or never mind.

So the structure is:

• Ne razumijemo simbol = We do not understand the symbol
• a kamoli cijelu kombinaciju = let alone the whole combination

It emphasizes that if the first, smaller thing is already too difficult, the second, bigger thing is even less possible.

A very similar English pattern is:

• We don’t understand the symbol, let alone the whole combination.

In Croatian, negation with verbs is usually formed with ne + verb, written as two separate words:

• razumijemo = we understand
• ne razumijemo = we do not understand

This is normal for most verbs in Croatian.

Examples:

• Znam = I know

• Ne znam = I do not know

• Vidimo = we see
• Ne vidimo = we do not see

So ne razumijemo is just the regular negative form.

Razumijemo is the 1st person plural present tense of razumjeti or razumiti depending on standard/usage, but in standard Croatian the usual form is razumjeti.

Here it means:

• we understand

The subject pronoun mi = we is omitted because Croatian usually leaves subject pronouns out when the verb ending already makes the subject clear.

So:

• (Mi) razumijemo = We understand
• (Mi) ne razumijemo = We do not understand

The ending -mo is a common sign of we in the present tense.

Croatian is a pro-drop language, which means subject pronouns are often omitted if the verb already shows who is doing the action.

In ne razumijemo, the ending -mo already tells you the subject is we.

So both of these are possible:

• Ne razumijemo simbol.
• Mi ne razumijemo simbol.

The version without mi is more natural unless you want extra emphasis, such as:

• Mi ne razumijemo simbol, ali oni ga razumiju.
• We don’t understand the symbol, but they do.

Simbol is the direct object of razumijemo, so it is in the accusative case.

But simbol is a masculine inanimate noun, and in Croatian, masculine inanimate nouns often have the same form in nominative and accusative singular.

So:

• nominative: simbol
• accusative: simbol

That is why it looks unchanged.

Compare this with a masculine animate noun, where the accusative usually does change:

• nominative: student
• accusative: studenta

Because this phrase is also functioning as a direct object, it must be in the accusative singular.

The base form is:

• cijela kombinacija = the whole combination

But in the accusative singular feminine, both words change:

• cijela → cijelu
• kombinacija → kombinaciju

So:

• nominative: cijela kombinacija
• accusative: cijelu kombinaciju

This is completely regular for many feminine nouns ending in -a and adjectives agreeing with them.

No. A kamoli can be followed by different kinds of material, depending on what is being contrasted.

It can be followed by:

• a noun phrase
• a verb phrase
• sometimes a fuller clause

Examples:

• Ne mogu platiti kavu, a kamoli večeru.
  I can’t pay for coffee, let alone dinner.

• Nije pročitao članak, a kamoli knjigu.
  He didn’t read the article, let alone the book.

• Ne zna govoriti hrvatski, a kamoli pisati ga pravilno.
  He can’t speak Croatian, let alone write it correctly.

So in your sentence, a kamoli cijelu kombinaciju is one natural and compact use of the expression.

The comma helps separate the first statement from the emphatic follow-up introduced by a kamoli.

Croatian punctuation commonly uses a comma before linking expressions like this, especially when the second part adds a contrast or escalation.

So the structure is:

• first statement: Ne razumijemo simbol
• escalated continuation: a kamoli cijelu kombinaciju

The comma makes the sentence easier to read and reflects the pause you would naturally make in speech.

Not very naturally. It is best learned as a fixed expression.

If you tried to analyze it word by word, you would not get a neat English equivalent. In real usage, you should simply treat a kamoli as an idiom meaning:

• let alone
• much less

That is the safest and most natural way to understand and use it.

Yes, that is possible, but razumjeti and shvaćati/shvatiti are not always identical in nuance.

• razumjeti often means to understand in a broad, general sense
• shvaćati/shvatiti can mean to grasp, to comprehend, or to realize

In many contexts they overlap, but razumijemo is very natural here because the sentence is about understanding a symbol and an entire combination.

So the original sentence sounds completely normal.

A useful pattern to remember is:

• Ne + verb + object, a kamoli + stronger/bigger object

For example:

• Ne poznajem osnovna pravila, a kamoli sve iznimke.
  I don’t know the basic rules, let alone all the exceptions.

• Ne mogu riješiti jedan zadatak, a kamoli cijeli test.
  I can’t solve one problem, let alone the whole test.

Key things to watch:

• use ne before the verb
• put the object in the correct case
• use a kamoli to introduce something even harder, bigger, or less likely

That will help you produce natural sentences of the same type.