One side of mower wont turn

Hi Lori, The links below are YouTube videos that might get you out of trouble... Also there's videos down the right side of the links that may help as well.............. CHEERS..
How to test a lawn mower Key switch....
How to test lawn mower key switch
How to test a solenoid....
How to test lawn mower solenoid
How to test lawn mower electrical safety switches....
How to test lawn mower electrical safety switches
Shows all safety switches disabled....
Disable all lawnmower safety switches

check the connecting rod see if it came off

Does it hum or make a binding noise when you push the lever? There are by-pass valves on the pump. If there is no noise then that's more than likely your problem. If you hear a soft grinding like sound at the wheel motor then it sounds like the motor is by-passing oil.

You might want to post this question in the lawnmower section so that the proper expert sees it.

each side has its own pump and it own release levers on the rear make sure the releae is ok

ther should be a turn buckle to adjust them to the same speed

take a good look at the linkage

Under the cover that covers the flywheel on the right hand side there is a connector that is likely unplugged,this grounds the coil when you turn off the key and there by shuts of the motor.If this is not the problem then you likely need a new ignition switch.

Check the hydraulic oil level for the hydrostat drives(if it has a reserve tank located under the seat. Some ZT's don't have the reserve tank. Don't over fill that tank. 1/4 inch above the bottom is all it needs.)

Also, check the steering arm bolts. Very often they work themselves loose and the arm doesn't pull the valve rod that controls the hydrostat unit.

THE GEAR ON THE SHAFT IS STRIPED OUT NEEDS A NEW ONE