^ My experience too. I always try to have excess battery capacity over what I actually need for that reason. More reliable and increases the lifetime of the battery significantly.
Best way is to set everything up and do a runtime test to see if running off one battery works for long enough.. and is reasonable < that is to say, only using something like half the battery's capacity.
If not, use two batteries or one larger capacity one. If you use two batteries, simplest will be to use a separate one for either piece of gear. If one piece of gear draws more current than the other, you might want to try the "Y" both in parallel to a common power line, which you then "Y" back out to both pieces of gear. That should balance the load pulled from the batteries.
The amperage of the charging wall wart is not really relevant to what you can power with the battery. In the case of charging, higher amperage from the wall wart (within safe charging limits) will simply charge the battery faster than a lower amperage wall wart.
Thanks. However: the above part is confusing. The Zoom's wall wart is just for powering the Zoom, it's not a "charging wall wart". Or am I missing something?
Not you, me. I thought you were referring to the Talentcell charging wallwart, not the one that powers the Zoom.
The Zoom's wall wart is rated for 2A output, so unless I'm missing something, that leaves 4A for other devices.
^ In light of that, this is technically true, but best draw less than the max capability of the battery as discussed.