One of the more persistent (and annoying) theories on the case of the Zodiac killer is that a man named Joseph Bevilacqua, who served time in the US military and had been stationed in the Presidio during the Zodiac era and who moved just outside of Florence, Italy a couple of months before the first Monster attack, was both the Zodiac killer and the Monster of Florence.  I do not agree in any way with this line of reasoning, although there are admittedly some MO similarities between the two killers.  However, when you look at the signature aspects of these two killers the case for the Zodiac also being the Monster of Florence falls apart.
As far as MO is concerned, the proponent of this theory correctly points out that both the Monster and Zodiac were lover’s lane killers.  However, as you get deeper into the case of the Monster of Florence, there is the issue of the 1968 murders in the town of Lastra a Signa, which lies northwest of the city of Florence, and their relationship to the Monster.  The murders of Barbara Locci and Antonio Lo Bianco were committed in a known lover’s lane.  After much analysis (which is too detailed to get into here) it is widely believed that while the same gun was used in the Locci-Lo Bianco murders as in all of the later Monster crimes, the Locci-Lo Bianco murders were not committed by the Monster of Florence himself (although the Locci-Lo Bianco murders would be linked to his crimes in 1982).  It is also widely believed that the Monster was ritualistically reproducing the Locci-Lo Bianco crimes when he also attacked in lover’s lane areas and also killed amorous couples beginning in September of 1974.  The point being that the MO of attacking in lovers lane areas may not even be original to the Monster but may have been copied from a previous, unrelated crime scene.  Therefore, it seems that the Monster, unlike Zodiac, was potentially not even killing people in lover’s lane areas by his own design.
Therefore, this aspect of the Monster crimes does not really match what Zodiac did as neatly as one might have you believe.
Zodiac’s most obvious signature behavior was the fact that he loved to write boastful, taunting letters to the press, mainly to the San Francisco Chronicle.  These letters often included cryptograms and bomb diagrams.  Zodiac also gave himself his nickname.  While the Monster definitely wrote letters, most notably to Prosecutor Sylvia Della Monica after his last crimes in 1985, none of them was of the same nature as the Zodiac letters.  And none of them contained cryptograms or bomb diagrams.  He also did not name himself the Monster of Florence:  His nickname had been created by reporter Mario Spezi.  The Monster likely wrote three letters in 1982, but he sent them directly to the police and the goal of these letters was to create misdirection in the investigation, not to boast, etc.  To wit, the Monster likely created what is known as the “Sardinian Trail,” whereby he led the police down a blind alley investigating the Sardinian clan who had actually murdered Locci and Lo Bianco in 1968 in a vain effort to find the Monster of Florence.  
In short, Zodiac needed to boast to the entire Bay Area.  The Monster did not have such a need in the area surrounding Florence.  There were no, “This is The Monster speaking…” letters.  Therefore, while both killer wrote letters, the content and goal of the letters were not the same.
Finally, let’s talk about the most important difference between the Zodiac killer and the Monster of Florence.  According to profiler Richard Walter, Zodiac was a non-sexual, power-assertive killer.  Zodiac killed for a sense of power, not to fulfill any sexual or anger needs.   He simply killed people then walked away.  He never took the type of sexual “souvenirs” from his female victims that the Monster did.  He never mutilated any of his victims.  The Monster, as I said in an April 2021 interview with the Italian media, was a piquerist, which in turn makes him a sexual anger killer, who is much different from the power obsessed killer that Zodiac was.  Finally, Zodiac dealt with living victims and interacted with them, although generally in a limited way, while they were still alive.  The Monster always shot and killed his victims before approaching them (except for Stefania Pettini, which was likely a mistake he committed, and quickly corrected by stabbing her viciously to death, at his first murder scene in 1974).  
There is no “evolutionary process” whereby one goes from a non-sexual killer to a sexual killer: You are either one or the other.  In fact, as I have said before, if the Monster of Florence and the Zodiac killer are ever determined to have been the same person, then this would make profiling obsolete, since profiling says that the Monster and Zodiac are, by definition, very different types of killers regardless of their MO similarities.  Whoever was the Zodiac killer should not have been the Monster of Florence, and vice versa.
There is one possibility that I cannot rule out and that is this: It is conceivable that Joseph Bevilacqua was the Monster of Florence but not the Zodiac killer.  Since profiling rules out him having been both, we must look at the most likely possibility.  The Monster of Florence was a necrophile of the Type IXa, as defined in the textbook Necrophilia by Anil Aggrawal.  This means that he was somebody who murdered a victim in order to mutilate them.  Of interest to me is the fact that Bevilacqua, when he transferred to Italy, was stationed at the Florence-US military cemetery near Scopeti, which was the site of the Monster’s last crime scene in 1985.  Bevilacqua also inserted himself into the trial of Pietro Pacciani, who was accused of being the Monster, saying he saw Pacciani in the vicinity of the crime scene. 
Necrophiles like being near cemeteries because it brings them close to the dead.  The question I have always had is this: Did Bevilacqua request to be transferred to the cemetery from San Francisco, or was he stationed there purely via a decision by the military to place him there?  If he requested the assignment rather than being assigned it, then this makes him of more interest to me as a possible suspect in the Monster of Florence case but not as both the Zodiac killer and the Monster.

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