Can't tell you much about the Inspiron Z series, either, except that like Studio Z, it's the "thin and light" take on Dell's budget Inspiron line using Intel ULV chips.
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The 14z and 15z seem a lot like Acer's Timeline series, actually. The 11z, as you can tell by the way it's designed, looks more like a follow-up to Dell's Inspiron Mini netbooks, on the other hand. Gotta love that super-wide trackpad on it.