Learn Croatian: Išli smo oko jezera i kratko zastali. - We went around the lake and paused briefly.

The base verb is stati, which means to stop or to stand. The prefix za- often indicates a short deviation or a brief, temporary action. By adding it, we get zastati, which means to pause or stop for just a short moment, rather than stopping completely.

Why isn't there an auxiliary verb before zastali, such as smo zastali?

When connecting multiple past tense verbs with i (and) that share the same subject, you do not need to repeat the auxiliary verb. The smo from Išli smo carries over automatically to zastali.

Why do we use the imperfective verb išli followed by the perfective verb zastali?

This mixes aspects to show how events unfolded. Išli smo (we were going) is imperfective, setting an ongoing background action. The perfective zastali (we paused) acts as a sudden, brief event that happened during that background action.

Which case is used for the word jezera, and what triggers it?

Jezera is in the genitive case. The preposition oko (around) always requires the following noun to take the genitive case, just like many other prepositions showing spatial relationships (like pored or iznad).