Deleting the existing Zynq block and adding a new one will give you the possibility to apply the presets. However, any configuration change you did before (e.g. adding gpio, ddr ports etc.) will be lost. Even if there are connections created between blocks - these will be deleted then.
Actually I stored a preset from a design which is a bit more complex and use this for other designs. Not used things can be switched off later. As long as my understanding of the Zynq block isn't that good, I prefer starting with something validated instead of searching to much in the settings.
