Could you also use "ze" here?
Thank you! Sometimes I don't know whether I made a mistake or should report the sentence :)
Why is it "wie" singular instead of "wiens" plural, since zijn is plural?
There is no plural form of "wie". "wiens" means "whose".
So you use "wie" for both the singular and the plural, as you can see here:
So when I have to use "die"?