The Append option isn't what is needed here (the way Append is used in the posted code will result in two zip files concatenated together)

As you've demonstrated, the MultiStream option is the way to create a single zip file with multiple members.

Regarding ExtAttr, as you say it is a number, not a string. Plus it isn't being set to "0666<<16" by default as the documentation states -- I will look into that.

Paul