Although it seems similar, Shadow Imprisoning Mirror is different from Skill Drain.
1.) With Shadow Mirror it still can't attack directly. The first effect of Zombyra (the one where it can't attack directly), is continuous. Shadow Mirror cannot prevent continuous effects.
2.) With Zombyra at 1700 ATK and after Shadow Mirror is activated, his attack will still be 1700.
If you had Skill Drain instead, it would be yes all around. Remember, with Skill Drain, all things are possible.
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