isVowel
static int isVowel(const char*);
return z[1] == 0 || isVowel(z + 1);
while (isVowel(z)) {
while (isVowel(z)) {
while (isVowel(z)) {
while (isVowel(z)) {
while (isVowel(z)) {
isVowel(z + 1) &&