Complex sentence: In 2005, the circle motif returned (with streaks of light and sparkles formed using the ABC logo) with the introduction of the new "Only on ABC" slogan, but in 2006-2007, the largest change to ABC's appearance occurred.
Split into simpler sentences: In 2005, the circle motif returned (with streaks of light and sparkles formed using the ABC logo) with the introduction of the new "Only on ABC" slogan. But in 2006-2007, the largest change to ABC's appearance occurred.