ZFX does several things...
1. It reduces the drying time, which might be more important to someone in Seattle as opposed to Phoenix.
2. It allows multiple successive coats (for those Zaino-philes who are so inclined) to be applied without a waiting time.
3. It also looks better (subjective, but I think it does).
Since, in the past, you only used Z-1 once a season, ZFX gives you the catalyzing benefits with each coat. If you use ZFX, there's no reason to use Z-1.
-Jim
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1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
Looking for 76-79 Honda Accords