I spent 10 wonderful days in Zeldas appartment in July/August. It is very cosy and extremely clean - the terrace, however, is covered and not very bright, which for me made perfect sense since it was a perfect place to work.
The flat is located in a nice, calm and safe neighbourhood - but you can still reach the center of Naples within a few minutes by public transport and the sea is within walking distance. I can fully recommend Zeldas place, also because the communication with her and her sister who picked up the key when I left was cordial and totally uncomplicated.