OLDWICK, N.J.–(BUSINESS WIRE)– #insurance–AM Best has affirmed the Financial Strength Rating of A (Excellent) and the Long-Term Issuer Credit Ratings of “a+” (Excellent) of Zenith Insurance Company and ZNAT Insurance Company. The outlook of these Credit Ratings (ratings) is stable. These companies comprise Zenith National Insurance Group (Zenith) and are domiciled in Woodland Hills, CA.The ratings reflect Zenith’s balance sheet strength, which AM Best assesses as very strong, as well as its adequate opera