Isn't ZigBee a short range (about 100m) protocol used for home automation stuff?
Please note there is no second 5.8ghz antenna. This is taken from the FCC declaration. If you want to kid yourself that the 5.8 has diversity then please yourself. I would prefer to stick with the facts.
The wifi board you show has 1 x 2.4ghz antenna (internal) and 1 x 5.8ghz antenna (external). There is no second 5.8ghz antenna