In the deeper zoom, not only are the contours much closer together than in the base image (the "landscape" rises more steeply), but the palette used has smaller transitions. The palette used in the base image has a large step in colour values between adjacent contours, taking only 9 steps to go from deep blue to yellow.
If you use a single value step in just one of the three primaries from one contour to the next, you can still discern the difference but it is less obvious, appearing far more smooth. I would do this with a precalculated look-up table.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…