Sure you know, this is a really bad idea;) But if you want to register a domain that contains a fückinß umlaut, this solution will work for bind. But I start with a little explanation, you are not allowed to fill the bind configs with umlauts you should transform them to punycode.

Install transformation tool:

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apt-get install idn

Transform you domain:

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echo www.größte-scheiße.de | idn -a --quiet

The output will be: www.xn--grsste-scheisse-9sb.de

Now you can use the converted string of your domain in the bind configuration files.
If you are using putty please set your Translation to UTF8 otherwise idn will not convert your domain;)