ok not an easy task by any means lol!
You've got to remember the 6 factors towards star rating:
Release to the Wild - release a cheap animal to the wild as soon as you buy them (if you can afford it), peafowl's usually nice and cheap
Animal Happiness - this takes a while to build up, because as soon as you place the animals their happiness is only half full, best bet is to pause the game and build the zoo as early as possible
Number of Animals - kind of self explanatory, get as many different kinds of animals as possible, if you have AA it's quite easy to get a large mixed exhibit that can still fit into your 'Educational Exhibit' criteria
Educational Exhibits - make sure your foliage (and other animals if a mixed exhibit) come from the same area as your animal
Guest Happiness - the overall pain in the bum to get lol, one way is to make your guest area really small so they don't have far to go to get what they need to satisfy their happiness
Entertaining Animals - this one's always been difficult for me, I find primates and penguins to be the more entertaining, I place the toys near the edge of the exhibits but don't know if this makes a difference or not
Of course if you still have access to the money cheat all this requires is a lot of patience as you can build your entire zoo in January and wait out the year to iron out any problems