Ok, what I did.
The T-Rex scenario has one cool part: An area obviously made for the exhibit to go. I didn't do any terain leveling so that they couldn't attack the EIB. I researched T-Rex Care and Dinosaur Care before the Rexes were even at my zoo. When they were there, I put 'em in the exhibit. I did what the scientist said. In fact, I did more: I kept changin the terain and stuff till they got frowny faces, then hit Undo, and went to the next part. Oh, I did the terrain first, needed 'em to be somewhat calm before I started putting trees. Despite what the earlier person says, place Monkey Puzzle Trees in the exhibit: They are T-Rex's favorite plant, thus making it happier. Also, put in the shelter. Anyway, after that, make it hilly till they don't like it. After all that, just wait... Eventually they might breed.
Doing that, I succeded. I call myself the Tyrannosaurus Breeder.