Looking to go to Chester Zoo? Visit Cheshire Oaks Designer Outlet - Tourist Information Centre (SatNav post code CH65 9JJ) and buy your tickets there.
It's only a 5-10 minute journey by car to the zoo, so not much of a detour.
Cheapest price from the zoo website (after removing the voluntary donation) = Adult £16.30, Child £12.60, Concession £15.00, Family Ticket £53
Approx 11% discount
I know this has been posted a while ago, but these are up to date prices (phoned the Tourist Office today to check).
IMPORTANT! Cash only for tickets - plenty of ATMs though