In June 1941, Kapitan Mazhaiev served in the 123 IAP of the 10 SmAD.

The regiment was based at Imenin on 22 June 1941 flying Polikarpov I-153s. During the first day of the war, the unit claimed more than 20 victories while losing nine of their own in air combats. Pilots flew as many as 10-14 sorties; in one case, even 17 sorties were reported during the day.
Mazhaiev claimed one Bf 109 during the first day of the war.

Later in the war, he served as commander of the 123 IAP.

On 21 November 1942, the 123 IAP was renamed the 27 GIAP.

Mazhaiev ended the war with one biplane victory and a total of 6 and 1 shared.

Claims:

Kill no.	Date	Time	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1941
1	22/06/41		1	Bf 109	Destroyed	I-153			123 IAP
2	??/??/4?		1	Enemy aircraft	Destroyed				123 IAP
3	??/??/4?		1	Enemy aircraft	Destroyed				123 IAP
4	??/??/4?		1	Enemy aircraft	Destroyed				123 IAP
5	??/??/4?		1	Enemy aircraft	Destroyed				123 IAP
6	??/??/4?		1	Enemy aircraft	Destroyed				123 IAP
	??/??/4?		1	Enemy aircraft	Shared destroyed				123 IAP

Biplane victories: 1 destroyed.
TOTAL: 6 and 1 shared destroyed.

Sources:
Stalin's Eagles - Hans D. Seidl, 1998 Schiffer Publishing, ISBN 0-7643-0476-3
Additional information kindly provided by Ondrej Repka.