Two things that are not yet clear to me:
1) Do you want the coupon to have any other discount, too? Or do you simply want a coupon that gives free shipping only to orders of less than 30€ in the given ZIP range?
2) How shall the coupon discount be displayed in the invoice? Is is sufficient to simply show a shipping rate of 0, or do you need 3.99 shipping minus 3.99 coupon discount (for tax purposes)?
In the simple case (the whole purpose of the coupon is to give 0 shipping costs to orders below 30€ in the given ZIP range; no other discounts are given by the coupon; the invoice can simply display 0 shipping costs), I would do it as follows:
-) Give the coupon a value of 0€ like in your coupon1 image (you don't want any explicit discount handled by the coupon, just a different shipping rate which is handled by the shipping plugin)
-) In the shipping method, use a rule
Name="Free shipping with coupon"; Coupon=="COUPON 1"; Amount<30; 50001<=ZIP<50008; Shipping=0
That rule needs to be placed before a rule that gives the normal 3.99€ shipping rate for orders <30€ in that ZIP range. Compared to your screenshot, you need to set shipping cost to 0.
Best regards,
Reinhold