Zentangles don't require anywhere near the same amount of patience that stabby stabby art does. There are a lot of rules that are meant to be followed according to the official creators of this form of art but even they don't stick to them. Otherwise new patterns known as "tangles" would never be created. 
The main rule of this type of art is to use square tiles. I have yet to find a pad of paper in squares so  just stick to the standard paper sizes because I cannot be bothered to make an A4 sheet of paper into a square. 
The best part about this type of art is that anyone that can hold a pen and follow instructions can do it. 
See where it all began
Check out some of mine below.