Can I take Zatoxin Duo and vitamin B complex at the same time? Am I overdosing on vitamin B2, for example?

Yes, you can. According to current medical literature, there should be no adverse interactions between these preparations that are harmful to health or the effects of drugs. The recommended Daily Intake of vitamin B2 according to the Institute of Food and Nutrition for adult women is 1.4mg. Its toxicity is not known because it is excreted in the urine at high doses. Between the use of the above preparations, it is worth keeping a few hours break, a minimum of 2-3 hours. I attach additional information that may be helpful: https://www.gdziepolek.pl/artykuly/czy-mozna-laczyc-leki-ze-soba