Time Zero had more saturated colors and a general teal/steel green cast to it. Looked really nice. Primary colors popped. It was extremely sharp too. 600 film was good as well but it was more consumer oriented. It had a generally warmer color palette with browns and tans. Also very sharp. I like the new film in its own rite but it is quite different than the pre-2008 stuff
...and, don't forget this, as its name suggests, the picture was before your eyes in no time. Instax film is slow compared with time zero. Not to speak of recent Polaroid film...
I bought my first SX70 in August of 1977. It was a lightly used first run model and I kept it until 2012. Time Zero arrived in the mid 1990's as Polaroid was shifting to the 600 cameras and phasing out the folders. The old film had great colors and a very special look, the 600 film was fine but the colors didn't have the same warmth as the older film. Also, you could use an old pen or other stylus to manipulate and draw around or on the image as it developed, that was lost with the introduction of the 600 films. I was recently gifted an Alpha 1, I briefly considered having it converted to 600 but decided to stay with it's original configuration.
Well, it was quicker than original SX-70 or 600. There was discernible image in about thirty seconds, as I recall, vs. close to two minutes for original SX-70/600, Kodak, and Instax.