Need to be away from other light sources, to be best effective. Don't hang them under the double fluoro.
They may attract more moths and stuff, but shouldn't attract more mozzies, as the mozzies are mainly attracted by heat rather than light. The zappers don't generate a lot of heat (less than a lightbulb). But once the mozzie are near, and see that wonderful light....
Clothing is also important to prevent mozzie bites. It may be macho to swim with only jocks on, but it's also mozzie bait.
My son has a full trunk lycra swimsuit that helps keeps the beasties off. As well as his own roll-on Aeroguard.
Like I said, if viral disease carried by mozzies are a problem, or even malaria, then a DEET-based personal repeelent is a must, as well as local measure to keep numbers down (like, no open containers of water for them to breed in). If ya live near a swamp, unless the local council treats it, ya can't do much about them except cover up and use repellent and zappers.
But prevention is much better than repellent for mozzies.
Cheers
Mick