input: Write a python function to generate an equation from given coefficients and variables.
  assert generate_equation([2, 3, 4], ['x', 'y', 'z']) == '2x + 3y + 4z'
  assert generate_equation([1, 0, -1], ['a', 'b', 'c']) == '1a + 0b + -1c'
  assert generate_equation([5, 6], ['m', 'n']) == '5m + 6n'
output: def generate_equation(coefficients, variables):
      terms = [f"{coeff}{var}" for coeff, var in zip(coefficients, variables)]
      return ' + '.join(terms)