Single contact multiple accounts

Single contact multiple accounts

We have an individual, consultantjohnny@email.com, who is a technology consultant that works with several of our customers.  How can I add this contact "consultant Johnny"  to CRM/DESK to be associated with multiple accounts. (Company X, Company Y, Company Z). 

Specifically So that when Johnny sends an email into zohodesk, we can link the ticket to the correct company/Account . For example Johnny may send in an email regarding company A, and then shortly after he  sends in another email to Zoho desk for an issue with Company Z.  We need to be able to keep the tickets linked to the correct Zoho Account.

ALso, when sales people need to correspond with Johnny they need to be able to put the notes In the correct Zoho Account, and send emails to Jonny and have them linked to the correct Zoho Account.

how can we accomplish this task.

~ron