Hi Jon,
I think your zimmerit looks fine, especially for the first time out. You've successfully captured the somewhat erratic look of the real thing, and home made always looks more personal and unique.
I cannot comment on the accuracy of your particular tank, but I can offer one tidbit on zimmerit in general. Around big bolts, round vision port protrusions, and similar obstructions, zimmerit was sometimes applied in a "star" pattern, as if radiating from the center of the protrusion. When applicable, this provides an opportunity to break up some of the vertical columns and add a little more character to the zimmerit.
I also like the chipping. Good job!
-Doug