composite measure and MANOVA

Hello, I need to create a composite measure of two scales and was wondering if I need to convert the scores from the two scales to Z-scores first and then average the two or can I average the two scales without conversion if both scales have the same scale of measurement?

Also, if I end up using the converted z-scores in a MANOVA as one DV, do the rest of my DV's also need to be converted to z-scores?