Currently, these formulas are in D1, E1, D2, E2, D3, E3, D4 and E4,
respectively:

=IF(LEFT(A1,1)="1",IF(LEFT(C1,1)="0",LEFT(C1,3)&MI D(C1,5,3),"000000"))
=IF(LEFT(A1,1)="1",IF(LEFT(C1,1)="0","0000000","0" &LEFT(C1,2)&MID
(C1,4,4)))


=IF(LEFT(A2,1)="6","000000","000000")
=IF(LEFT(A2,1)="6",IF(LEFT(C2,1)="0","0"&LEFT(C2,3 )&MID
(C2,5,3),"0"&LEFT(C2,2)&MID(C2,4,4)))


=IF(LEFT(A3,1)="1",IF(LEFT(C3,1)="0",LEFT(C3,3)&MI D(C3,5,3),"000000"))
=IF(LEFT(A3,1)="1",IF(LEFT(C3,1)="0","0000000","0" &LEFT(C3,2)&MID
(C3,4,4)))


=IF(LEFT(A4,1)="6","000000","000000")
=IF(LEFT(A4,1)="6",IF(LEFT(C4,1)="0","0"&LEFT(C4,3 )&MID
(C4,5,3),"0"&LEFT(C4,2)&MID(4,4,4)))


How can I create one formula by nesting each pair of formulas?