Is the second sentence below grammatically correct? If not, why so?
We are looking for the house the windows of which are broken.
We are looking for the house of which the windows are broken.
Is the second sentence below grammatically correct? If not, why so?
We are looking for the house the windows of which are broken.
We are looking for the house of which the windows are broken.
Yes. Both are grammatically correct - and the second more idiomatically usual than the former.
If you want to use the first it might be improved by putting a comma after "house".