I have tried but it doesn’t seem one can use both cloudflare email routing and a google workspace custom domain at the same time. Please if there is a way to do this, it would be very helpful thanks.
There is no way to use them both at the same time for the exact same (sub-)domain.
If you are willing (and able) to switch Google Workspace to run on a sub-domain instead, such as e.g. @google.example.com rather than @example.com, that could be a way.
Welcome to the Cloudflare Community. 
It is not possible to use Cloudflare Email Routing while using another email service on the same domain.
What you need to do is set up google to be using a subdomain as a “user alias domain” on GSuite.
So you’d have your regular email accounts as [email protected], [email protected] etc. and you’d set up a second domain at Google like email.example.com as a “user alias domain”. This would allow users to get emails at [email protected] and [email protected] as far as google is concerned.
Then on Cloudflare DNS you can set the MX record for example.com to use Cloudflare routing and it should route [email protected] to [email protected] while you should set up the MX records for email.example.com to point to google’s mail servers.
If you would want [email protected] to route somewhere else at this point you could easily have it route/forward to wherever you want it to using Cloudflare routes or email workers.
I also have a completely separate mail provider running on mail.example.com and I route emails to that one for my users who don’t want gmail but want a regular IMAP/POP3/webmail server. I also route some users, [email protected] to [email protected] to a non G-suite gmail account. They can then either utilize the GSuite provided SMTP to send mail as [email protected] from their [email protected] account (granted they have a gsuite account) OR they can use the SMTP that is provided by mail.example.com and send emails through that route.
Only important part is to have the correct DKIM for both GSuite and the hosting service provided SMTP so they both pass sender verification.
You can also use a third party such as mailgun to send/receive emails via pointing the root MX record to their mail handler.
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