Translation:He cannot become used to
Is there a reason why "he is not used to" is not accepted ?
For "he cannot become used to", wouldn't a more correct translation be "yeye hawezi kuzoea";
The word kuzoea is a word that indicates a progress, so it can be translated to "become used to". So "he is not used to" would be translated as "he has but become used to" or "hajazoea"
The basic verb "kuzoea" carries the meaning of "be used to", or "become accustomed to". Therefore I think both translations to be acceptable. I am not a linguist, but there's a difference in meaning between the stative verb (a resultant state, the one being used) and the infinitive (the one you suggest).