Hydroquinone 4% & tretinoin 0.05% in combination: How should it be done, & would this exacerbate irritation/inflammation?

I'm hoping to get info about this for skin pigmentation/overall condition improvement in young, Caucasian skin. Both drugs are known for irritation. Would mixing them together make it worse? Some preparations add corticosteroid, but I've got visible veins & I'm reluctant to trust tretinoin to mitigate the skin atrophy potential. Also, should I mix them, or use one product a night, switching each night? Tretinoin contributes penetration enhancement, but I'm unsure of the irritant impact of that.