Welcome back Fountain :)
I usually build my entire zoo on pause, and the very last thing I do is add the animals and staff.
I put zoo marketing all the way up, and zoo entrance fee to $10.00 for adults, $5.00 for children.
I set all attractions to $5.00 and restaurants to $10.00.
I use only restaurants, no food stands, no picnic tables, no trash cans, and the only maintenance people are for the tank filters.
One thing I do that helps keep guests happy is place a row of flowerbeds along both side of the path between the path and the exhibits, and between the path and the decor/buildings.
This does several things, ups guest happiness (This area is so lovely!), keeps guests from wandering off the path and getting stuck in strange places (which REALLY decreases guest happiness), keeps animals from feeling over crowded even if there is clear fence all around the exhibit, and keep animals from escaping the exhibit, even dinosaurs cant escape a low stone wall if there is a flowerbed up against it.
And I always get the maximum number of guests (1000) in the zoo very quickly, with zoo rating usually 98, guest happiness around 98, animal happiness around 98.
I know that most people dont build zoos the way I do, I just wanted to share that in case any of it helps you figure it out :)