Whilst there are three separate models in the Srixon Z 65 range of irons, they all share the same heritage and design principles.

Like the three previous Z 45 irons the heads are forged from 1020 Carbon Steel to give the softer feel that better players will like.
The faces feature the same double laser milling process with one line parallel to the grooves and another at an angle to get the most spin possible.

The difference with the Z 65 faces is that the grooves are now 5% larger than before. They are wider because Srixon's machining process has improved to go closer to the legal limits and this will help the grooves dispel grass and moisture more easily and get a little more grip on the ball.
Finally all three models now have a revised version of the Tour V.T. Sole that uses a V shape design to generate the bounce.

Srixon say that this shape enables the club to move quicker through the turf and therefore not lose as much speed and when reviewing the similar V Sole on the Cleveland RTX-3 wedge it was generating more ball speed than a more traditional design.
It works by increasing the leading edge bounce and reducing the trailing edge bounce to create different sizes of V in the sole. The 'step' in the sole of the Z 45 irons has gone and is replaced with a little more heel and toe relief which not only plays well, but looks better too.

The size and shape of the V.T. Sole differs from one model to the next so let's focus on the individual Z 65 iron models now.
Srixon Z 965 Irons Review
The Z 965 iron is the blade version of the range aimed at single figure handicappers who want maximum control and feel.

Compared to the previous 945 the sole is a little narrower and the lines are smoother on the trailing edge of the toe section.
This is a common theme as the muscle on all three Z 65 heads has been moved from the heel side of centre to more towards the toe.

This not only helps forgiveness in terms of MOI, but also in CG position, which sholuld move more towards the centre of the face.

On the longer irons from 3 to 6 iron there is a tungsten toe weight to help with this process, which a lot of companies do, but I think I would prefer not to see it and believe that my classic swing or some mysterious force was making the magic happen instead.

Certainly the 965 did feel marginally better than the 945 through the set but there was not as much of a noticeable difference compared to the other models, so if you already have 945s and are happy with them then you may not need to upgrade.
Srixon Z 765 Irons Review
The Z 765 irons on the other hand are a worthy upgrade as they feel better and will be the ones that I can see most mid to low handicap players gravitating towards.

They combine forged feel and better player looks with a muscle back design that features enough peripheral weighting to add some forgiveness without sacrificing too much feel.

The V.T Sole is a little wider as you might expect and the same sole and muscle back changes apply to the middle child in the Z 65 iron family.

The feel sounded and felt that little more solid than the Z 965 right through the bag due to that semi-cavity back design.

I probably even preferred the 46° P wedge from this set over the bladed 965 version for this reason, even though there is not much between them for low single figure players.
The 51° A wedge is a blade style, which is a little surprising given the rest of the set design, but the oversize head and chrome finish blend in well with the set and provide an alternative to a standard 50° or 52° Cleveland RTX-3 wedge that also has the same V-Sole design.

The longer irons are very playable and when you hit it right then the 4-iron felt really good. I would say that if you are just below a 100mph driver swing speed then you may want to look at the higher launching Z 545 4-iron as the 765 version will need a decent amount of speed to get it high enough to land and stop on the green.

Overall the Z 765 ticks a lot of the right boxes for better players. It has clean looks with a nice sized top line, the right amount of forged feel, a bit of forgiveness, a touch of offset and it all comes together to make you feel like a better player without admitting that you need the help it offers.
It's clean and simple and does the job well with little fuss and other brands could learn from this approach.
Srixon Z 565 Irons Review
Finally, we come to the Z 565 irons, who are the best fed of the family, as they have the largest top line and the deepest backside, or cavity as it is preferred to be known.

Right down to the short irons the deep undercut cavity draws the CG back to add forgiveness and increase the launch angle.

The forgiveness is also greater thanks to the thicker perimeter weighting than the 765 around the edge of the head.

The only difference to the other two models is that the face uses a high-strength SUP10 steel face insert to increase ball speeds.
As you will probably know by now, this means decreasing lofts to keep the peak height the same for each iron, so the 565 irons are 1° stronger than the 765 in the 4 to 8 irons and 2° stronger than the 965 in the 5-iron to PW.
The Z 565 is where you noticed the better feel most over the previous Z 45 irons as it felt a lot softer. The longer irons launch it on a nice high penetrating flight and even with the bigger cavity they still sounded like a solid forged iron.

The faces on shorter irons might feel a little jumpy to better players than the other models, but most will find them delivering the combination of forgiveness and distance that they are looking for.
The Z 565 are ideal for mid handicapper upwards and the great thing is that they still look similar to the other models so if you want to blend them in with any of the other models then they won't sound, feel or look out of place.
Srixon Z 65 Irons Summary
Whilst each of the three models are perfectly fine sets in their own right, the opportunity to blend them is obvious, provided you watch the distance gaps as the lofts are not the same across the board.
Mid-handicappers could look at the 565 from 4 to 8-iron and then swap in the 9 and PW from the 765, which are the same lofts in both sets.

Better players in either the 965 or 765 might want to move up a set for the 3 and 4 irons for that extra launch and forgiveness and for most 765 players I would recommend doing that for the 565 4-iron.
The great thing about all three models is they are forged so you get great feel, but they also look good and bring in elements of necessary forgiveness without any fuss. Maybe they are a little understated and therefore could slip under most people's radar, but seek them out as the Z 65 range is one of the best in the market.