Lookup (One-to-Many)
Standard lookup fields create a one-to-many relationship by pointing a field in the child module to a record in the parent module. Up to 5 lookup fields may be used in filter criteria per rule/workflow/Blueprint. Lookup fields cannot be added to Tasks, Meetings, or Calls modules (Zoho CRM help: Types of Custom Fields).
Advanced Lookup: When searching in a lookup popup, users can add up to 10 columns to the search window and apply multi-field filters (Zoho CRM help: Types of Custom Fields).
Subforms (One-to-Many Embedded Tables)
Subforms embed a table of related records directly within a parent record's form. They do not require a separate linked module—they are part of the parent module's layout. Subforms may optionally include lookup fields that reference other modules (Marks Group: Custom Field Types). Examples: Line items in a Quote, Stakeholders in a Deal.
Client Scripts can interact with subform data, and as of Q4 2025, client script support was extended to subforms (Zoho CRM 2025 highlights).
Multi-Select Lookup / Many-to-Many (Enterprise+)
The Multi-Select Lookup field establishes a many-to-many relationship by auto-generating a linking module (join table) in the background. Each module can have a maximum of two multi-select lookup fields, one of which may be self-referencing (linking the module to itself, e.g., to model a manager/subordinate hierarchy) (Zoho CRM help: Types of Custom Fields).
Connected Records (2025 Feature)
"Connected Records" was introduced in 2025 to allow users to associate records from different modules that share a common customer context (e.g., linking a Deal, a Case, and a Project to the same customer relationship). This provides a contextual aggregation view without requiring formal relational links (Zoho CRM 2025 highlights).