[Zen count practice] trouble when alternating odd and even number count

#1
Fellow zen counters,
How to practice zen count? Hi-lo in 20s a deck is not a problem for me. But once I get to zen count, the jump from odd number to even number got me stuck for so long. I can bearly do it for 40s a deck. Please enlighten me on how to get good at odd-even number counting.
Thanks,
 
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