As you know, it is possible to create collections of activities that you can then share with your students. It is also possible to share one or more collections with your colleagues so that they can use it with their own students. The process for sharing a collection with colleagues is different from the one used to share with students.
Sharing with other teachers is done by exchanging a URL link that you generate and send to your colleague. The URL link can then be shared with any teacher. This includes a colleague working in a different school, provided that he or she is a Buzzmath subscriber.
Once the URL is received, the teacher who opens it can view its contents first and then duplicate it in their own collections. And once the collection is duplicated, it can be modified as needed.
Note that collections are not collaborative and sharing only allows the recipient to create a copy of a collection from another user. If the original creator of the collection modifies it, the changes will not be reflected in the shared and copied version. He or she will have to share it again in order to provide the new version of the collection, so that it can be copied again.
Here is how sharing works in detail: How do I share my collections with my colleagues?