Setting up an SLA based on a Salesforce organization or user

Overview

How to establish a Zendesk SLA (Service Level Agreement) based on information applied to a user or organization in Salesforce.

Must have a Professional or Enterprise level Zendesk account (for the SLA feature)
Must have installed the Zendesk for Salesforce app
Must have a Group or Professional edition of Salesforce

First it's important to configure user and organization syncing in Salesforce. There is the option of a one-time sync or an ongoing sync. The ongoing sync will likely be the best choice in order to keep your users and organizations in Zendesk up-to-date with your Salesforce account.
When you have set up the syncing, you need to select a pairing to modify its sync settings. Your options will be to sync Accounts and Organizations, Leads and Users, or Contacts and Users. The choice is whether to have an organization or specific user trigger an SLA.
Finally, you will want to establish a Tag or Field mapping in Salesforce, which will be the basis of your SLA as an SLA can be established by the addition of a tag on a Zendesk ticket. That tag can be added from a user profile or a user's organization.

If you want to create a mapping with Tag Mapping, this will allow you to choose one of your existing fields in Salesforce to automatically populate a value as a domain name, a tag, or a note associated with the Zendesk user. With this option you would be able to set a specific tag to a user or organization, which would then be applied to that user's tickets, thus used to apply an SLA.
The other option would be to create a Field Mapping (done in the same place) which would allow you to set a specific field in Salesforce to map to a specific user field or organization field in Zendesk. This is sometimes (depending on workflow) a better option as fields automatically apply the tag value associated with the field, so the same end result occurs. However, fields can also be updated in the future, which will then reflect in your tags. Because tag mappings do not remove tags, only add them, changing the tag value of a tag mapping would only add an additional tag, not also remove the older tag.

Once you have both the sync and mapping established, you will want to set up the Zendesk SLA. You have already established the tag value based on the user or organization field mapping above, therefore you can now add this information as a tag condition for your SLA policy: