sed question: lower-to-upper case

[Greg Klein]

I would like to use sed to change certain (not all) words in a text file
from lower case to upper case.  For example, the selected words to be
changed might be all words that contain one or more lower case z's in
them (like 'zebra').  Any ideas?

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Greg Klein				| Microcomputer Electronics Corp.
voice:	(206)821-2800 x702		| 12421 Willows Rd, NE
uucp:	...!hplabs!hpubvwa!mechp!klein	| Kirkland WA, USA 98034
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