The best way I've found to open these up, is by inserting something from one side, and pushing these tab out on the other side.
I've previously used a paperclip, but it bent and was a little large... today I modified a needle by cutting the eye. I actually left the fingers a little long - I have three modules to disassemble, and one of the fingers broke off part way through the operation... they can be much shorter!
Using this tool, insert it, and try to put a finger either side of the tab... then just push!
You will need pliers or a sacrificial surface to push against - it's quite a stiff operation.
Once you've got the tab flush with the outer body, you've actually blocked yourself from getting to the other tab. So revert to a screwdriver to open the tab the rest of the way.