You need to speak to a doctor or pharmacist about this question. Never risk your health by mixing medicines you are unsure about.
Check with your doctor or pharmacist/chemist - if you take zantac - I guess you have stomache/digestive problems and asprin can make this worse.
Please get professional advice, about this. Also the voltaren may have another dose of pain killer in it and you say you are taking asprin.
Life is too precious to risk your health on not seeking proper advice. I hope your health soon improves.