One possible issue is galvanic corrosion. In certain conditions, if dissimilar metals are in contact with each other the more electronegative metal will corrode at a greatly accelerated rate, effectively the same situation a a metal/metal battery. This can be a particular issue if you have steel studs or other interests in a non-ferrous casting.
Indeed sacrificial zinc anodes are used to protect thing like boat hulls and submerged piles from corrosion and this is why galvanising is such effective corrosion protection, even if the zinc surface layer is scratched through to the base metal the galvanic effect will continue to provide protection.
Equally zinc is a fairly reactive metal which relies on a passive oxide layer for corrosion resistance so anything which disrupts this layer can cause very rapid corrosion. Even quite weak acid can strip galvanising in a few hours.
Also with any cast part you should consider shrinkage as a potential source of tolerating issues although this should be apparent from new. Equally inadequate design of a casting can generate high residual stresses and other defects which can cause failure over time.