There are various strategies to do this. Chances are that neither a single itinerary nor four one ways will be the best option but a combination of two or three itineraries.
You can easily book "open jaws" for the long haul. I.e. AMS->MSY + UIO->AMS as a single ticket that will cost about about $1000 (in September). Sometimes throwing in extra short leg in the target region is almost free and sometimes it's ridiculously expensive. You need to try a few combinations.
It helps if the destinations are served by the same airlines (or close partners) and if there are direct connections between the stops. Your sequence is quite tricky, so this is not going to be easy.
At a rough guess I would book this as an open jaw and two one ways. $1000 for the two long hauls, $150 for MSY->HAV and maybe $500 for HAV->UIO. If you can change the sequence this may get cheaper.