If you are setting up Office 365 with custom domain you will be asked to configure name server pointing to below in the domain admin page. In our case it will be Google domains registration page.
If you altered name servers into Office 365 it wont help you to propagate DNS entries with Google domain management tool since you have handed over responsibilities to Microsoft Online DNS services.
⚡ Note – You required to enter DNS record in Office 365 but not in the google domain registration console.
You could achieve adding custom domain entries buy following path or finding domains in search in Office 365 admin portal.
☛ Home –> Setup –> Domains –> New Custom Record
⌛ It may take many minutes to propagate around the world based on the condition and you could check success of propagation with tool ViewDNS.