It doesn't seem like you can zero both the current work offset and the active work offset by just clicking or entering values in the DROs on the Offsets page.
I don't have a copy of mach3 in front of me, so I may word something incorrectly here.
Your terminology is incorrect. The "Current Work Offset" is describing the offset number, 1, 2, 3, ....
The "Active Work Offset" is describing the offset g-code, G54, G55, G66, ...
There are two sets of DRO's on the offset page.
1) The Offsets
2) The machine position in Work Coordinates (with offset applied).
The machine position is the Machine coordinate position - the Offsets. If you zero the offset, the position DRO's will display Machine Coordinates. Machine Coordinates can only be zeroed by Referencing (homing) the axis.
If you zero the position DRO's, what your doing is setting an offset (unless the position is machine zero). So this will change the offset DRO's.
When you zero the offsets, you'll change the position DRO's to show Machine Coordinates.
You might want to watch the tutorial video on homing, limits and offsets, which explains how offsets work.