It brings together the traditional Zen enso, or circle, and elements from the logo of Amida Trust (which IZT is part of).
The enso is an image that's become reasonably well known in the West, although perhaps its meaning is less known. It represents the ultimate trancendent reality.
The Amida Trust logo is a sunset: the sun and clouds. The sun here represents Amida, which can be considered that aspect of ultimate reality which comes to us, and which we can relate to.
The clouds in this image represent the kleshas. A klesha is a mental state of mind which clouds judgment (anxiety, fear, anger, jealousy, desire and so on) and prevents us from seeing Amida clearly. This is the ordinary human reality, there is something which is perfect in love and wisdom, but so much of the time it is hidden from us by clouds which rise from our karma.
The new IZT logo introduces this element of humaness to the perfect Zen enso. The two horizontal lines are like the clouds which obscure the bright light of the sun.