Ask about what genus zoas they are. Then look up the genus. If it's one that produces palytoxin, then it's best you avoid them. You should know that most cases of palytoxin poisoning that are reported have to do with improper disposal of zoa rocks. The ONLY way to safely kill/sterilize rock that has had zoanthids on it (that I know of) is to soak the rock in bleach. Microwaving, boiling, leaving it out to dry, will all just leave the palytoxin on the rock or get it into the air.
I assure you, aquarium water does not just "become toxic and evaporate into the air." Toxins/everything are left behind in the process of evaporation, hence why it's recommended you top off with RODI water as opposed to saltwater. Should water drip onto the ground, wiping the area with water, then a dilute bleach solution (which breaks down the palytoxin) and then water again should reduce the palytoxin to non-harmful levels. The first water wipe is to dilute the toxin, the bleach to break it down, and the third wipe to get rid of the bleach. If you have bleach-proof floors (tile, concrete, brick, etc.), you can just wipe down with bleach.
What you should actually be worried about, is water getting aerosolized. That's when water is churned up and becomes a fine spray, which contains all the salt/toxins that you want to avoid. This can be avoided by securing any outlets that may spray (return lines, in tank pumps) that may come in contact with the air during a water change, thereby minimizing the chance of water aerosolizing. Keep the tank's cabinets closed to prevent dogs/small children from accessing the sump and playing with the water.