A common situation: sales know a customer by its trading name, but the invoice needs to go out under its full legal entity name. For example, a business trading as TAPS is legally registered as Tavern And Pub Society Limited. Sales want to search for and work with TAPS in Zoho CRM; finance needs invoices in Zoho Books to show Tavern And Pub Society Limited. This is genuinely easier to solve than it first appears, and it's almost entirely handled on the CRM side.
Create or rename the Account using the name your sales team actually uses day to day, in this example, TAPS, rather than the full legal name. This is what reps will search for and recognise.
Add a note to the Account record with the full legal entity name, Tavern And Pub Society Limited in this example. This matters because finance, or anyone searching CRM, might only know the business by its legal name rather than its trading name, and CRM's search picks up note content, so a search for either name finds the same Account.
The same note field is also a reasonable place to record a related but separate entity, for example a known parent company, if that relationship is useful context for anyone working the account, even where a formal Parent-Child link (below) isn't set up for it.
Zoho CRM supports Parent and Child Accounts, which suit a different but related situation: where a group has multiple genuinely separate legal entities, each with its own contacts, but the group relationship itself is worth tracking. A commonly used example is a group structure where several brands sit under one parent, each with their own separate contacts and billing, but someone working one brand benefits from seeing it's linked to the others.
Each child Account remains its own distinct Account in CRM, and crucially, remains its own distinct legal entity in Zoho Books too, each still invoiced separately under its own correct legal name using the approach below. The parent-child link just makes the group relationship visible and navigable in CRM, so someone working one entity can see it's related to the others and knows to check before, say, assuming a contact from one applies to another.