I love making z fold cards they are so simple and do not require a lot of measuring but you still get a interesting card.
This is a card I made for my granddaughters 6 Birthday I used stickers along with the number 6 I cut out from my silhouette.
The little girl sticker I have had forever and the antique lace trim sticker is a dollar tree sticker!!!.
I often see Double Z fold cards and the measurements are usually for smaller a2 cards which I don't normally make but it is simple to make them any size you want. First you always cut 11 inch pc of paper the next measurement is what ever size you want your finished cards length to be. I wanted my card to be 7 inches in length when finished. No matter what finished length you always score at 5 1/2,and 2 3/4 on the 11inch side. The next step is just to fold in a accordion style with a hill and valley . The extra strip at the bottom is cut 11x 1 1/2 you score exactly like you did the base then adhere to the card starting with the longest section first.
This is a quick and easy card don't be afraid to give it a try.