With regard to ERA bricks:
There's no intrinsic reason the Zulfiqar could not be deployed with ERA. It could be mounted along the skirts and while the angle of the glacis might mean that ERA would also have to applied to the lower glacis unlike on the T-72 that shouldn't pose any problem (the British did the same on their Challys in Iraq IIRC). The face of the turret provides a nice flat mounting surface where good coverage could be attained, unlike on the Samsam where there are holes in the coverage because the M-60A1 was never designed to accommodate ERA. Bricks could even be applied to the side of the turret stowage boxes, providing additional protection outside the 60-degree frontal arc in the same manner as the Chinese Type 99.
Iran doesn't even have to use the Kontakt-1; the double-thickness ERA seen on the Samsam would probably have increased performance against long-rod penetrators since there is a bigger distance between the flyer plates which in turn induce more pressures on the incoming projectile.
With regard to RHA vs composites:
I can't offer any definitive conclusions, but I can suggest a few possibilities I've considered.
First, the term 'composite' armor is a broad definition since it literally includes any combination of materials; a peanut-butter and jelly sandwich could be considered composite armor, but I wouldn't trust it to protect my tank! On the other side of the spectrum are composites like arrays made up of titanium plates embedded in urethane covered with ceramic facing plates and a kevlar spall liner. In other words, 'composite armor' can cover a wide array of potential materials and effectiveness and doesn't point to a specific level of effectiveness just by itself. There's also questions of spacing, and orientation that affect the performance of the array but is independent of the materials used.
Despite the uncertainty when talking about composites, I think we can all agree that the use of exotic materials is a precondition to a modern armor array even if it does not guarantee it alone; RHA is just to heavy and too vulnerable. The original Zulfiqar-1 prototype was built with rolled RHA plates that didn't have any real protective value; they were just structural walls for the design of the prototype. The same thing could be true with the Zulfiqar-3 and is supported to some degree by the limited photographic evidence we have.
For instance, we can see inside the inverted turret here
; it's clear from the shadows cast and the relative position of the gun-mount that the turret-walls are RHA plate.
That being said, we don't know what stage of manufacture or overhaul the turret is in. RHA plate is used in almost every tank as a structural element and doesn't precludes the use of additional materials hidden away from view. While there are no visible modules or pockets in the turret which would be used for this purpose (as with the Leo, T-72 or Type 99), there might still be composites obscured from view behind the steel face (as with the Abrams).
The logic behind the assertion that the Zulfiqar-3 has composite armor originates from the configuration of the armor. When you're using RHA you want to maximize the LoS thickness between you and the threat; because it's homogenous, more material means more protection. This means you end up with something like the M-60 which is often described as having a 'needle nose' turret for exactly this reason. Laminate arrays don't benefit from this and are difficult to construct in the curved shapes found in RHA turrets. This means you end up with somethinglike the Abrams. Logically, since the Zulfiqar-3 has this same construction technique, it stands to reason that it also stemmed from similar design constraints (aka some form of laminate armor). Assuming this is true, the armor would probably include some sort of alumina ceramic (relatively cost-effective as far as ceramics go), steel and/or aluminum, maybe some titanium or rubber in between. I doubt really expensive materials like some of the harder ceramics or tungsten would be used because of their cost, and depleted uranium is out of the question at this stage.
Given the overall visual similarity between the M1 and the Zulfiqar-3 I'm not sure how much credence the above hypothesis should be granted though. It's just as likely IMO that the similarities stop at their visual appearance.
The use of composites doesn't necessarily need to follow this design path though. For instance, Soviet arrays with steel/aluminum reflecting plates suspended in urethane would easily have made it's way into the Zulfiqar-3 given their relative simplicity and Iran's experience with T-72s. This could actually be the source of Catsoo's assertion that it uses "reactive armor under the turret skin". I can't see explosive reactive armor (ERA) being used under the turret, but use of non-explosive reactive armor (NERA) such as 'bulging' armor is well documented.
I alluded to this above, but even if we were to know all the materials used we still wouldn't know the effectiveness of the armor because so much of the effectiveness is tied to their configuration within the turret. For instance, three layers of ceramic tiles stacked together and placed directly on top of three layers of titanium plate, and then placed on three layers of rubber would probably be less effective than a smaller array consisting of intelligently spaced plates of semi-hardened and mild-steel. Thus, knowing that the Zulfiqar-3 uses alumina ceramic in conjunction with aluminum is less important than knowing how they come together.