43021 ÷ 4 = 10755 R1
Alright, let's work through the division of 43021 by 4 step by step.

Step 1:
4 goes into 4 1 times with a remainder of 0.
Write down 1 as next digit of of the result. 
Result so far: 1
Subtract 4 from 4 to get 0.
Bring next digit (3) of the dividend behind the 0 and repeat the process: 3 / 4

Step 2:
4 goes into 3 0 times with a remainder of 3.
Write down 0 as next digit of of the result. 
Result so far: 10
Subtract 0 from 3 to get 3.
Bring next digit (0) of the dividend behind the 3 and repeat the process: 30 / 4

Step 3:
4 goes into 30 7 times with a remainder of 2.
Write down 7 as next digit of of the result. 
Result so far: 107
Subtract 28 from 30 to get 2.
Bring next digit (2) of the dividend behind the 2 and repeat the process: 22 / 4

Step 4:
4 goes into 22 5 times with a remainder of 2.
Write down 5 as next digit of of the result. 
Result so far: 1075
Subtract 20 from 22 to get 2.
Bring next digit (1) of the dividend behind the 2 and repeat the process: 21 / 4

Step 5:
4 goes into 21 5 times with a remainder of 1.
Write down 5 as next digit of of the result. 
Result so far: 10755
Subtract 20 from 21 to get 1.

The final result is 10755 with a remainder of 1.