Whenever a case is getting deleted check if it has the contact is related account // If it is related to the account and contact then throw an error saying "can not be deleted"

@venkateswarlu Allipudi

Check the below trigger :

trigger PreventCaseDeletion on Case (before delete) {
    // Set to store IDs of Cases being deleted to minimize the query scope
    Set<Id> caseIdsBeingDeleted = Trigger.oldMap.keySet();
    // Query to find Cases that are being deleted and are related to both an Account and a Contact
    List<Case> casesWithAccountAndContact = [
        SELECT Id
        FROM Case
        WHERE Id IN :caseIdsBeingDeleted
          AND AccountId != null
          AND ContactId != null
    ];
    // Set to store the IDs of Cases that meet the criteria for prevention
    Set<Id> preventDeletionCaseIds = new Set<Id>();
    for (Case c : casesWithAccountAndContact) {
        preventDeletionCaseIds.add(c.Id);
    }
    // Loop through the Cases in Trigger.old to find matches and prevent deletion
    for (Case c : Trigger.old) {
        if (preventDeletionCaseIds.contains(c.Id)) {
            // Prevent deletion by adding an error to the Case record
            c.addError('Cannot be deleted because it is related to both an Account and a Contact.');
        }
    }
}