Please fix or implement research as a franchise wide thing, not per zoo.
I'm literally on the fence on this issue. I do believe the vet research needing to be redone for each zoo is fair in franchise because of the progression and because its based on animals you currently have in your zoo.
But on the other hand I think it would also be fair (and a reasonable compromise) to have the mechanical research carried over in full or in pieces. This would allow you to start a new zoo with a different theme for example and start building/decorating from the getgo with the researched theme rather than having to come back and rework things once you have researched. Alternatively allowing you to pick 1-3 fully researched mechanics/themes when you start a new zoo - provided you've researched them in another zoo already - could also work.
I think a contributing factor to this effect is how easy it is to make money off of few species and few number of animals of those few species. It gets unproportionally difficult to maintain finances with more animals and species. It should be balanced to be harder to generate money off of smaller zoos and the increasing difficulty with larger zoos toned down.It makes the start of the next franchise boring. Put in a camel and a turtle, run at 3x speed while researching everything, erase when done and use the 500k earned while researching to start real zoo. Dull couple of hours.