Zij betaalt veertig euro.

By itself, zij can mean either she or they.

In this sentence, it means she, because the verb is singular: betaalt.

• zij betaalt = she pays
• zij betalen = they pay

So the verb form tells you which meaning is intended.

Both zij and ze can mean she.

The difference is mainly stress:

• zij is the fuller, stressed form
• ze is the common unstressed form used in everyday speech

So Zij betaalt veertig euro and Ze betaalt veertig euro can both mean the same thing. Using zij may sound a little more emphatic, contrastive, or simply a bit more formal/written.

The z is like English z.

The tricky part is ij, a very common Dutch vowel combination. In standard Dutch, ij is pronounced roughly like the sound in English eye, though not exactly the same.

So zij is approximately like zeye.

A more exact pronunciation depends on region and accent, but that approximation is good enough for a learner at first.

Because it is the third-person singular present tense of betalen (to pay).

The present-tense pattern is:

• ik betaal = I pay
• jij betaalt = you pay
• hij/zij betaalt = he/she pays
• wij betalen = we pay
• jullie betalen = you pay
• zij betalen = they pay

So with zij meaning she, you need betaalt.

Because betaalt is a present-tense verb form, while betaald is the past participle.

• zij betaalt = she pays / she is paying
• zij heeft betaald = she has paid

This is a very common spelling point in Dutch:

• present tense, third-person singular: often -t
• past participle of many verbs: often -d or -t, depending on the verb

So here, betaalt is correct because the sentence is in the present tense.

It can mean both, depending on context.

Dutch uses the simple present tense more broadly than English does. So:

• Zij betaalt veertig euro can mean She pays forty euros
• It can also mean She is paying forty euros

If Dutch wants to be extra explicit about an ongoing action, it can use:

• Zij is veertig euro aan het betalen

But in many normal situations, the simple present is enough.

This is the normal Dutch word order for a basic main clause:

subject + finite verb + rest of the sentence

So:

• Zij = subject
• betaalt = finite verb
• veertig euro = amount being paid

That is very similar to English:

• She pays forty euros

Dutch main clauses also follow the verb-second rule, which means the finite verb usually comes in the second position. Here the subject is first, so the verb comes right after it.

After an exact number, Dutch normally uses euro, not euro's:

• één euro
• twee euro
• veertig euro

This is standard Dutch for amounts of money.

You may sometimes see euro's in other contexts, but after a numeral, euro is the usual form.

No. In this sentence, veertig euro is given directly as the amount paid, so no preposition is needed:

• Zij betaalt veertig euro.

If you want to add what she is paying for, Dutch often uses voor:

• Zij betaalt veertig euro voor het boek.
  = She pays forty euros for the book.

If you want to say who receives the money, Dutch can use aan:

• Zij betaalt veertig euro aan de verkoper.
  = She pays forty euros to the seller.

So the basic sentence needs no preposition, but extra information may add one.

Yes. That is very natural and common in everyday Dutch.

• Zij betaalt veertig euro = correct
• Ze betaalt veertig euro = also correct

The version with ze is often what you will hear in normal speech. The version with zij may sound more emphasized, clearer, or a bit more formal depending on context.