When you patch a Solaris 10 server it applies each patch to each zone one-at-a-time . So if you have 3 zones and it takes 1 minute to apply a patch on global zone then it will take another 1 minute each to apply on other 3 zones. Thus in total you will be spending around 4 minutes to apply single patch on the server. You can imagine the time it will take to apply a 300 patches bundle.
From Solaris 10 10/09 onward you have got an option to patch multiple zones in parallel.