If my opponent used Latios GX's "Clear Vision GX" attack on me, could I use Bonnie to allow my Zygarde-GX to use its GX attack?
No, you cannot. Although Bonnie would normally let Zygarde-GX re-use its GX attack, the effect of Clear Vision GX is on Zygarde-GX and that still prevents using *ANY* GX attacks.
Source: TPCi Rules Team (2019-09-05)

Relevant cards

Note: All applicable cards may not be listed below.
SM11_223
SM11_223
SM11_243
SM11_243
SM11_78
SM11_78
SM6_103
SM6_128