Zoo Tycoon Cheat Codes

Cheat Method via File Edits
1. Open config.ztd with winzip or another compression tool.
2. Open Economy.cfg with notepad or wordpad.
3. Search for cZooDooRecyclingAmount and change the number to whatever you want. This will be the profit for every recycle you do. Normally you recycle around 8-12 times per month.
4. Also, look for cKeeperCost which should be 800. This is the salary you pay your zoo keepers. Change it to something lower and your expenses will decrease dramatically.
5. If you want more money at start of the game, edit zoo.ini with notepad or wordpad and find a line called MSMaxCash. Change that to whatever you want and you can start out with a couple of million.

Note on changing exhibit names: Let the game auto name your exhibit, then change it, otherwise you may lock up the game.

All Scenarios
Name a guest Akiyama to unlock all the scenarios

Hatch an Egg
Name a guest Eggman and all dinosaur eggs will hatch after a scientist checks it.

Unlock the Triceratops
Name one of your exhibits Cretaceous Corral. This will unlock the Triceratops.

Money - Instant 10K
Press Shift+4 [like typing the $ symbol], and you'll get an instant $10,000.

Unicorn
Name one of your exhibits Xanadu. This will unlock the Unicorn.

Get 2X Donations
Name an exhibit Microsoft.

Cutt Off Salaries
Name a tour guide Rosalie and all your tour guide's salaries will turn to zero.

DoDo Bird
Name an exhibit doflopnok.

Yellow Brick Road Footpath
Place a lion tiger and bear in the same exibit to unlock the yellow brick road footpath.

Dodo from Alice and Wonderland
Name a dodo Mr.Dodo than the dodo will turn in to the dodo bird from Disney's Alice and Wonderland.

Santa Claus
Change your date to Dec 25th.

Easter Bunny
Change your date to Easter Sunday.

April Fool
Change your dat to April 1st.

Hobo
Change your date to Jan 8th.

Halloween @ The Zoo
Set your system date to October 31st.

New Year's Baby
Change your date to Dec 31st.

Yoda
Name a guest Yoda - Yoda will enter the park.

Funny Animals
Use the following names on the appropriate animals:

[Hippo] Fat: Two hippos Sum [Bear] Deer: Bear gets Free from Exhibit [Lion] Nan: Get a baby from a male lion [Unicorn] Larry: get size of a Dinosaur [Dinosaur] Unicorn: One Horn [Dodo] Doflopnok: Unlock the White Dodo [Panda] Blackly: Unlock and turn in to a Red Panda [Bongo] Bad: Turn in an Okapi [Okapi] Tall: Get tall as a Giraffe [Yeti] Bigfoot: Unlock the Bigfoot [Yeti] Bentley: Turn in to Spyro's friend, Bentley [Reindeer] Rulpoln: Red light nose [Reindeer] Dancer: Dances with a female Reindeer [Croc] Agent 9: Always happy [Monkey] Agent9: Turn in to Spyro's friend Agent9 [Ape: Chimpanzee or Gorilla] Borneo: Unlock the Orangutan [Ape] Kangaroo: Unlock the Wallaby [Gorilla] Mountain: Unlock the Mountain Gorilla [Tiger] Nope: Unlock the Magnet the Polar bear [Tiger] Dog: Unlock all Worker Dogs and Great Dane [Kangaroo] Shelia: Turn in to Spyro's Friend Sheila the Kangaroo [Penguin] Sgt.Byrd: Turn in to Spyro's frend Sgt.Byrd the flying Penguin [Sgt. Byrd] Fly: Fly out of Your Exhibit and Your Zoo

source from About.com