regexprep(YourCellArray, {'^0+(?=\d)', '(?<=_)0+(?=\d)'}, {'', ''})
This takes care not to replace an all-zero sequence with emptiness -- e.g., '00_14' will be converted to '0_14' and not '_14'. The code can be simplified a little if it is certain that a string of all 0 will not be present.
The code does not assume that the values are 2 digit; the code could be simplified even more if it was certain that all values were 2 digit.
regexprep(YourCellArray, {'^0', '_0'}, {'', '_'}) %2 digit case only
