Here's an example of when you may want to use multiple Zaps and filters to get around a required field.
Let's say I have a Zap that sends new Google Contacts to Salesforce as Leads. Salesforce requires a Company name, but sometimes my Google Contacts won't have a company name, and I'm okay with that. To help get around that, I'll set up two Zaps:
In my first Zap, I set up a filter so that the Zap only continues to the next step when there is a company in Google Contacts. Because of that, I map the Company field across when setting up the action.
In my second Zap, I just copy my first Zap and make two changes: I change the filter condition to "Does not Exist", and manually enter in a default company name since there won't be one in Google Contacts.
The end result is that when I have a company name from Google Contacts to send to Salesforce, it gets sent across. When I don't, a generic dummy name is used instead to avoid errors.