I'm not sure why would publish the horizontal accordion to a tab show position? You can simply publish it to custom_1 instead and then publish slides to s5_ha_X positions. It's not a good idea to publish a rotating module inside of another one. Keep in mind that Zoka has specific styling for the horizontal accordion module that doesn't transfer to other templates either; the default styling of the module would be used.
No the other way round:
S5_tabshow is published on Custom_1 and on s5_tab2 I tried to publish the accordion ....without any success yet (currently I use another instance of Tabshow instead) but still think an Accordion like the one of Zoka would be nice.
Anyway I currently can't see anything when I publish the Accordion on s5_tab2. I only mentioned s5_ha_X to make clear, that I checked that the position is "known" by the xml-file and it is handled as if it has content meanwhile I do not see anything.
Perhaps (presumably) there is anything I do wrong in setting up the according but I didn't figured itout what that might be.....