SEC Form 4

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* ZAX STANLEY R (Last) (First) (Middle) 21255 CALIFA ST. (Street) WOODLAND HILLS CA 91367 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol ZENITH NATIONAL INSURANCE CORP [ ZNT ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X Director 10% Owner X Officer (give title below) Other (specify below) President & Chairman
	3. Date of Earliest Transaction (Month/Day/Year) 09/08/2005
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) X Form filed by One Reporting Person Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	09/08/2005		F(1)		65,614	D	$64.32	404,474	D
Common Stock	09/08/2005		M		178,638	A	$23.625	583,112	D
Common Stock	09/08/2005		F(2)		51,787	D	$64.49	531,325(5)	D
Common Stock								337	I	By Son(3)
Common Stock								337	I	By Daughter(3)
Common Stock								356	I	By Daughter(3)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Employee Stock Option (right to buy)	$23.625	09/08/2005		M			178,638	(4)	03/14/2006	Common Stock	178,638	$0	0	D

Explanation of Responses:

1. 65,614 shares of common stock previously held by the reporting person were tendered to the issuer in payment of the aggregate exercise price of $4,220,323 for the Employee Stock Option based on the closing price of $64.32 per share for the common stock on the New York Stock Exchange on September 8, 2005.

2. In connection with his above described exercise of options, Mr. Zax requested Zenith to withhold a number of the newly acquired shares of Zenith Common Stock sufficient to reimburse Zenith for withholding taxes. The withholding tax was $3,339,769 and 51,787 shares valued at $64.49 per share, the average of the high and low prices of $64.99 and $64.00, respectively, on the New York Stock Exchange on September 8, 2005, were withheld by Zenith.

3. These securities are held by the reporting person as custodian for the reporting person's adult children. The reporting person disclaims beneficial ownership of these securities, and this report shall not be deemed an admission that the reproting person is the beneficial owner of such securities for pruposes of Section 16 or any other purpose.

4. Employee stock option exercisable for a total of 1,000,000 shares became exercisable as to 200,000 shares on each March 15, 1997, 1998, 1999, 2000 and 2001.

5. A summary of this filing follows: Mr. Zax's direct holdings of Zenith Common Stock prior to his surrender of shares in payment of the aggregate exercise price for his employee stock option exercise on 9/8/05 was 470,088. 65,614 of these shares were surrendered on 9/8/05 and Mr. Zax received 178,638 shares of Zenith Common Stock from his exercise of options on 9/8/05. The total number of Zenith shares withheld for taxes was 51,787 and as a result of the exercise of his stock options, Mr. Zax's direct holding of Zenith Common Stock increased to 531,325 shares as of September 8, 2005.

	/s/ Stanley R. Zax	09/09/2005
	** Signature of Reporting Person	Date
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