Can I use 'as long as / provided (that) / providing (that) / on condition (that) / only if' instead of if in zero conditional?



You possibly can in some, but only 'if' is possible in, for example, If you heat ice, it melts. In the traditional zero conditional, 'if' has a similar meaning to 'whenever'. The other expressions have a far stronger idea of exclusive conditionality, 'if and only if'.

You could say 'As you heat ice, it melts', but that is not a conditional sentence.