Not the answer you were looking for: You'll need Lollipop [Android 5.0] to run in 64 bit.

Here's some discussion: https://boinc.berkeley.edu/dev/forum_thread.php?id=10728 . My Nexus 7 is ARMv7, so per the last post in that thread, it requires 32 bit science apps.

The IF question is, whether OET1 was compiled to run in 64 bit on Android, then it would be most likely ZIKA is as well. If your device is rooted, you may be able to look into the BOINC data directory and figure it out.

And it's overrated, once upon a time WCG techs determined the performance is like 4-8 percent up on 64 bit, but such compiles can even run slower. BOINC has a test facility to figure this out on a host by host basis [do not know if actually deployed at WCG].