What to do with Leads coming in from an existing Account

What to do with Leads coming in from an existing Account

Hello
We have an integration with our webinar/content host and any new sign ups come as new leads in Zoho 
It's not impossible for these leads to be working for an existing account, just someone we have yet to interact with 
In this scenario, would we keep them as a lead, or convert them to a contact to connect them with their associated account? 
Thank you :)