Zinsco circuit breakers have issues with improper heat dissipation, which can lead to burning of the circuit breaker itself. Further Zinsco breaker boxes use an un-anodized or un-plated aluminum bus bar arrangement. In moist climates this can lead to excessive oxidation, whereby the bus bars actually reduce in size as the oxidation process continues. This can lead to loose connections, which may result in arcing or burning at the bus bar/circuit breaker connection point.
We highly recommend if you have a Zinsco breaker box, that you replace it immediately.