Thanks for the suggestions, but the zoo is maxed out already, 300+ animals, all the Critical and Endagered species, a 5 star marine show, a 5 star jeep tour and two 5 star skytours, 100% guest & animal happiness but the maximum number of guests the game allows is set in the program code at 120 people and I was trying to change that, more than improve the zoo.
Pengiuno put me onto a Hack to change the program code to allow more than 120 guests and I eventually got it to work by editing the "GuestMgr.xml" document that lives inside one of the massive zipped "x15100......ztf" files.
When I found it I edited it in notepad (then re-saved, re-zipped and re-saved it) to change just two characters, the maximum guests per star, and I increased mine from 30 to 80 guests per star and they are now flooding in....up to a max of 400 guests now instead of 120.
Thanks for the suggestions though and thanks again Penguino for the tip!!