Is this sentence grammatically correct?
He doesn't only like football but also likes tennis.
and if it's wrong, why so?
Specifically, is there any problem with omitting the subject in the second clause?
Also, is there any problem with the verb form likes?
Best Answer
I would rephrase the sentence as
in the style of the first of the examples here. This rephrasing avoids repeating the verb after but also if it is the same verb that came before the not only (compare with the second example in the link, where there are two different verbs).
Note that here the not only... but also... construction is used to amplify the object of the sentence, which essentially is of the form "He likes THIS". That's why it is not necessary to repeat neither the verb "like" nor the subject "he" inside the object.