Is there a regular expression that can recognize positive even numbers (including numbers with leading zeros, but excluding "0000" numbers)?

Like I said in the title, I am having a hard time writing this particular regular expression.
Any help would be much appreciated.

My best attempt in trying to solve this problem was writing this:

^([0-9]*[1-9][0-9]*)*[02468]$

But this regular expression can’t recognize a number like "002". Then I have tried this:

^([0-9]*[1-9][0-9]*)*[02468]*[02468]$

Now regular expression recognizes "002", but also recognizes "000" (only zeros) and I can’t avoid that happening.

In conclusion, I am failing again and again in writing a regular expression that can recognize positive even numbers (including leading zeros, but excluding "000" – numbers with only zeros) like:

2, 001234, 00123400, 002, 20, 16 etc.

Thank you in advance.

>Solution :

You could use a positive lookahead for any digit except 0:

^(?=.*[1-9])[0-9]*[02468]$

• (?=.*[1-9]) – positive lookahead for any digit except 0
• [0-9]* – any digit repeated 0 or more times
• [02468] – any even digit

Demo