Got it, well, even so I would still vote ZSL.
Chiroptera: Rodrigues fruitbat, Seba's short tailed bat. (Colchester apparently keeps 0 bats)
Rodentia: Malagasy giant jumping rat, Australian water rat, brown rat, beaver rat, naked mole rat, cape porcupine, Patagonian mara, guinea pig. (Colchester apparently keeps 0 rodents)
Marsupialia: Goodfellow's tree kangaroo, red necked wallaby. (Colchester has only 1 species)
Procaviidae: Rock hyrax. (0 hyrax kept at Colchester)
Sciuridae: Swinhoe's striped squirrel, prarie dog. (Colchester apparently has 0 squirrels)
Orycteropodidae: Aardvark.
Xenartha: Giant anteater, Southern tamandua, Linne's two toed sloth, large hairy armadillo. (Colchester lacks an armadillo to complete the Xenartha)
Macroscelides: Short eared elephant shrew. (0 elephant shrews at Colchester)
Tenrecidae: Lesser hedgehog tenrec. (0 tenrecs kept at Colchester)
All of these plus the EDGE species program / conservation output that I mentioned above put ZSL miles ahead of Colchester IMO.