Very few do
When ZTR's were new you could adjust the valve movement at the transmission and the length of the control rods so the lap bars were balanced.
They stopped doing that years ago
There is some limited adjustments and specific detailed instructions in the Toro service manual which is a free download from the Toro mowers web page.
You will need the Toro product number from the ID tag on the mower.
A worn belt , sticking tension arm or bad idler pulley will all cause an imbalance between the two drive units
