Learn Dutch: Zij zouden meer belasting moeten betalen.

In Dutch, you express "should" (as advice or moral obligation) by combining the conditional verb zouden (would) with the modal verb moeten (must). Literally, it translates to "would have to." Because the subject is the plural zij (they), we use the plural form zouden.

Why are there three verbs in this sentence, and how is the word order decided?

The sentence uses one conjugated verb (zouden) and two infinitives (moeten and betalen). In a main clause, the conjugated verb takes the second position. All other verbs are pushed to the end of the sentence. When placing multiple infinitives at the end, the modal verb (moeten) generally comes directly before the main action verb (betalen).

Could zij mean "she" in this sentence?

No, because the verb zouden is plural. If the sentence was about "she", the verb would be singular: Zij zou meer belasting moeten betalen. Also, the stressed pronoun zij is used instead of the unstressed ze here to put emphasis on the group—meaning they are the ones who should pay more, as opposed to someone else.

Why is belasting singular when in English we often say "pay more taxes"?

In Dutch, belasting is very commonly used as a singular noun when talking about tax in general. While the plural belastingen exists, the singular form is the most natural and frequent choice for a general statement like this.