Learn Turkish: Bazı sorular çok zordu. - Some questions were very difficult.

Bazı means "some" and is used as an adjective right before a noun, like in bazı sorular (some questions). Bazıları is a pronoun meaning "some of them" and stands on its own. If you wanted to use the pronoun instead, you would drop the noun and just say Bazıları çok zordu (Some of them were very difficult).

Why does "sorular" have a plural suffix? I thought we don't use plurals after quantity words.

Good memory, but there's an exception! You drop the plural suffix -lar/-ler after numbers (like iki soru - two questions) or specific quantity words like kaç (how many). However, with indefinite adjectives like bazı (some) and bütün (all), you must use the plural suffix on the noun. So it has to be bazı sorular.

Since "sorular" is plural, shouldn't the ending be plural too, like "zordular"?

It doesn't have to be! In Turkish, when a plural subject is non-human (like objects, animals, or concepts like "questions"), the verb or adjective usually stays in the singular form. Adding the plural ending to make it zordular isn't strictly wrong, but zordu is the standard, natural way to say it.

How does the word "zordu" work here to mean "were difficult"?