What are the better ways to code this nested conditional structure?

I would use R as an example:

# x is an object
# condA(x), condB(x) and condC(x) evaluate x and return TRUE or FALSE
# The conditions must be evaluated in the following orders.
#   For e.g., when validating for an random object being a number larger than 5,
#   you always need to evaluate whether it is numeric first,
#   only after which can you evaluate whether it is larger than 5.
#   Trying to evaluate both at once will cause an error if it is non-numeric.
# process1() and process2() are two different procedures
if (condA(x)) {
  if (condB(x)) {
    if (condC(x)) {
      process1()
    } else {
      process2()
    }
  } else {
    process2()
  }
} else {
  if (cond(C)) {
    process1()
  } else {
    process2()
  }
}

This way I need to specify each of the processes more than once, and repeat the chunk of evaluating condC(x), which I feel clumsy doing so. Any suggestion for a more elegant way of coding this structure, so that I need to mention each of process1() and process2() only once, without disrupting the order of evaluations as stated in the above code?