Hi, I am just getting around to answering my emails . . . so many!!
You have to cut yourself some slack. I saw your work . . . it's all beautiful. If I were to make any comment . . . I would say to draw your tangles more deliberately. Zentangle is not like any other art form. You want to draw every LINE deliberately, enjoying watching your pen create each line. The patterns fill the spaces created by the string. The string is just a suggestion and not a demand to where you put your tangles. You may start to place your tangle in one area, but maybe you want to finish that space with another tangle or leave it blank.
I tell my students that if you are doing the tangle "Tipple" - the one that looks like a sink full of bubbles - you want to draw each bubble slowly and not so much round as beautiful.
These pens are somewhat pressure sensitive so if you press a little harder on one side of the bubble and let up on the other . . . you create a rhythm of sorts . . . like music. If you played piano pressing every note the same, the result would be less than pleasant. If the weight of your penstroke was on the same side of each bubble, it creates a "shade" and adds to the pattern. You can do this to every pattern. Static . . . when doing the zig zag lines . . . the first zig is a light line, the next is heavier . . . consistently all the way down . . . then repeating the same pattern on each consecutive line. So simple, but very dynamic.
Practice, enjoy, hold it at arm's length OFTEN and admire your own work and never compare it to ANYONE'S. Just enjoy the process. Good Night, best, Maria