Move the 6 to the Zip bay. Jumper as Slave. Install the 80 and the 10 in whichever order you wish, in the normal ATA brackets. Jumper them as Master and Slave. It doesn't matter which is which.
Boot up, format, partition, install, copy as needed. When you are booting from the 80 and have everything removed from the 6, shut down and remove it from the Zip bay.
Or pull it's power connector and leave it as an unpowered backup drive. Power it up once a month for an easy document backup, then disconnect again. Your system will be quieter with fewer drives powered up.