Is the VMS homogeneous or a composite work?

[MarcoP]

Touwaide compared the Voynich manuscript with an "iatrosophion". You are not allowed to view links. Register or Login to view. elaborates on the meaning of the word:

An iatrosophion, widely used in Byzantine and Ottoman Greece, was a physician's notebook of recipes and treatments or was the collective compendium of classical and Byzantine medical and pharmacological texts consulted in hospital settings. Some iatrosophia included medical cures and drugs, but also spells, exorcisms, magic, astrology, and practical advice.

From the description of You are not allowed to view links. Register or Login to view.:

Iatrosophion compiled and used by Greek healers and practitioners of folk medicine, perhaps including local clerics, from the 16th to 18th centuries, possibly in Crete. The volume is foliated in part, but largely paginated (pp. 1-815). There are many missing and unnumbered pages. Decorative head pieces in the earlier parts of the manuscript. The text is comprised of approximately 70 sections, written in at least five different hands. This volume contains extracts from Greek medical treatises and information on botanical remedies (with a few color illustrations of plants), pharmacology, popular cures, astrological medicine (with charts), lists of "good" and "bad" days for phlebotomy, magical script, Cabalistic symbols, Zodiacal signs, pseudo-Solomonic pentacles, invocations of angels and demons, amuletic texts, spells, and prognostications. 

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I think that also a housebook / hausbuch could be a good parallel. For instance, see the table of contents of You are not allowed to view links. Register or Login to view..
1. A iatromathematical calendar book, including a perpetual calendar, times for bloodletting, a diagram of the twelve winds, influence of the stars on humans. 2. Discussion of the individual signs of the zodiac. 3. The four complexions. 4. A long section about geomancy. 5. The planets and their children. 6. Another astronomical section discussing the constellations and including cosmological diagrams.

Or the contents of You are not allowed to view links. Register or Login to view..
Art of Memory (in Latin). The planets and their children. Noble life (images only). Recipes (not only medical). Mining and metallurgy. War technology.

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From the e-codices description:

This manuscript, illustrated with numerous colored pen drawings, originated in a secular environment in Southern Germany or in Switzerland around the middle of the 15th century. It describes the signs of the zodiac, the planets, the four temperaments, and the four seasons regarding their influence on human health. This is followed by dietary guidelines primarily regarding bloodletting, but also regarding eating, drinking, sleeping, waking, resting and moving, as well as, in concrete terms, regarding bathing (illustration p. 101) or defecating (illustration p. 120). Most likely an amateur doctor with an interest in astronomy, from the Southern region of Germany, wrote the original text around 1400 and assembled it into a compendium. 

It is not entirely clear how much these works conform to some kind of planned design. They typically are not homogeneous (different subjects, different authors, sometimes different languages and different hands) but they are not random either.