How Genetically modified Mosquitoes work?

IN the past they used only male mosquitoes that could not impregnate the female mosquitos. However, this time they appear to be doing something different by introducing possibly both male and female mosquitoes whose larvae cannot reach adulthood so they cannot reproduce.

The problem with something like this could be that "Nature often finds a way" like in Jurassic Park movies.

So, it is theoretically possible that some kind of Frankenstein mosquito that is markedly different than the ones in nature might be the result. However, mosquitoes are so small that no one might know.

My question would be: "What would this difference be?"

Unfortunately, the answer might be "Anything!"

So also, what happens to birds and other types of insects that eat these genetically altered mosquitoes?

This is also a completely unknown answer as well.

So, this potentially might solve the Zika problem but spawn one or more problems much worse for the ecosystem including mankind and it is possible we wouldn't know where it came from for 100 to 500 years and maybe not even then. This is only part of the problem of genetically engineering ANYTHING.

Later: As I thought about this more I realized there are many ways to alter genetically anything. One way would be to expose the mosquitoes at some stage to radiation. Though this might prevent succeeding generations from growing to adulthood from larval stages it might be unknown at present what other ramifications might also result.