Create a method that performs complex DML operations with comprehensive error handling.

Parameters:

• accounts (List<Account>): List of Account records to process
• contacts (List<Contact>): List of Contact records to process

Returns:

• Map<String, Integer>: Map containing success counts for each operation

Requirements:

• Use DML insert operations for both accounts and contacts
• Handle DML exceptions gracefully for each operation
• Return a map with keys: 'accounts_inserted', 'contacts_inserted', 'accounts_failed', 'contacts_failed'
• Handle null inputs by returning appropriate counts
• Use try-catch blocks for each DML operation

Example:

List<Account> accounts = new List<Account>{new Account(Name = 'Test')};
List<Contact> contacts = new List<Contact>{new Contact(FirstName = 'John', LastName = 'Doe')};
Map<String, Integer> result = complexDmlErrorHandling(accounts, contacts);
// Returns: {'accounts_inserted' => 1, 'contacts_inserted' => 1, 'accounts_failed' => 0, 'contacts_failed' => 0}